For this puzzle of a cake, you'll need layers and layers of chiffon cake. You may think to yourself that there's possibly too much cake involved. And I'd agree with you-if you were already adept at making this. As it is, you'll thank me that you have extra with which to play. (See pages 166-167 for an idea on what to do with any extra.) Keep in mind that for a single cake, you're going to need 3 layers of pomegranate chiffon and 3 layers of key lime chiffon. Each layer will be ½ inch (12 mm) thick. Keep repeating this to yourself: 3 layers pomegranate and 3 layers key lime chiffon, ½ inch thick. Before you start, make sure you have the following handy: (1) cardboard cake rounds or something similar to hold all your layers; (2) toothpicks; (3) a large, very sharp serrated knife; (4) a revolving cake stand; (5) two 10-inch (25-cm) cake rounds; and (6) patience.

Photography by Tina Rupp

MORE CAKE RECIPES FROM 'BAKE IT LIKE YOU MEAN IT'

Makes 8 to 10 servings

FOR THE POMEGRANATE CHIFFON CAKES:

8 eggs, separated, at room temperature

⅔ cup (160 ml) vegetable or canola oil

1 cup (240 ml) pomegranate juice

1 drop red food colouring (optional)

3 cups (420 g) cake flour

1½ cups (300 g) granulated sugar

1 tablespoon plus 1 teaspoon baking powder

1 teaspoon salt

FOR THE KEY LIME CHIFFON CAKES:

8 eggs, separated, at room temperature

⅔ cup (160 ml) vegetable or canola oil

½ cup (120 ml) key lime juice, mixed with ½ cup (120 ml) water

3 cups (420 g) cake flour

1½ cups (300 g) granulated sugar

1 tablespoon plus 1 teaspoon baking powder

1 teaspoon salt

FOR THE BUTTERCREAM:

3 cups (600 g) granulated sugar

1 squirt fresh lemon juice

15 egg whites

pinch salt

2 pounds (910 g) unsalted butter, a little cooler

than room temperature

FOR THE ASSEMBLY:

1 cup (200 g) granulated sugar

Make the pomegranate chiffon cakes:

(25-cm) round cake pans by lining the bottom of each with a round of parchment paper that has been sprayed with nonstick baking spray. Do not spray the sides of the pans with nonstick spray. (Here, you don't want the cake to pull from the sides because the sticking helps keep the cake from collapsing before it cools and keeps the size of the cakes uniform.) Or use bottomless cake rings: Place parchment on a half sheet pan, spray the parchment, then plop the rings down onto the parchment so that none of the spray touches the sides.

In a stand mixer fitted with the whisk attachment, combine the egg yolks and oil and whisk until combined. Slowly add the pomegranate juice and food colouring, if using, and whisk until just combined.

In a bowl, sift together the flour, ½ cup (100 g) of the granulated sugar, the baking powder, and salt. Slowly add the flour mixture to the egg yolk mixture and whisk for 40 seconds until smooth. Transfer the mixture to a mixing bowl and set aside. Clean and dry the bowl and the whisk of the stand mixer thoroughly.

In the clean stand mixer bowl, whisk the egg whites until foamy. Slowly add the remaining sugar and whisk on high speed until stiff, white peaks form. (Make sure not to overwhip to the point of dryness or chunks.)

Using a large rubber spatula, gently fold the egg white mixture into the egg yolk mixture until fully combined.

Divide the batter evenly between the 2 prepared pans. Bake for 25 minutes, until the cake springs back when you touch it. Allow the cakes to cool completely. Then run a very thin, sharp knife run around the edge of each cake to release it from the pan. (If you release the cakes too soon, they may collapse. Patience!)

Make the key lime chiffon cakes:

Make 2 key-lime chiffon cakes by following the previous instructions for the pomegranate cakes, substituting the key lime chiffon ingredients (adding the key lime juice mixture to the egg yolks instead of the pomegranate juice).

Make the buttercream:

In a heavy saucepan, combine the granulated sugar, 1 cup (240 ml) water, and the lemon juice. Stir until the sugar is completely saturated so that it looks like wet sand and no dry spots can be seen. Place over medium-low heat and stir with a wooden spoon until the sugar has completely dissolved. With a pastry brush dipped in water, brush the sides of the pan to remove any sugar crystals clinging to the sides. Stop stirring, increase the heat to high, attach a candy thermometer to the side of the saucepan, and heat the mixture to 234°F (112°C).

Meanwhile, in a clean bowl of the stand mixer fitted with a cleaned whisk attachment, combine the egg whites and salt and whisk until they are foamy. When the sugar syrup has come to temperature, with the mixer on medium-high speed, very slowly and carefully pour the hot syrup down the side of the bowl and into the whisking egg whites. Once you've added all the syrup, increase the mixer speedto high and whisk until stiff peaks form and the bowl is cool to the touch. (This is important-if the meringue is warm, the butter will melt and the buttercream won't form a fluffy, smooth frosting. If this has happened, put the bowl in the freezer for a minute and then start mixing again.)

Slowly add bits of butter, about 2 tablespoons at a time. (There's a chance you won't need all of it.) When the buttercream starts to look like it's curdling, add just one more bit of butter and continue whisking for a few minutes until the texture becomes smooth and creamy. Keep at room temperature until needed.

To assemble:

In a microwave-safe bowl, combine the sugar with 1 cup (240 ml) water. Microwave at 50% power in 5-second intervals, swirling the bowl in between, until the sugar has completely dissolved into the water.

We want 3 layers of pomegranate and 3 layers of key lime chiffon-right now you have 2 layers of each kind. So once the layers are fully cooled and released from the pans, place them in the freezer for 5 to 10 minutes to firm them for easier slicing.

Place the first round of cake on a cake stand. Trim the top of the cake to make it perfectly level. Then, using a ruler, measure and mark the cake every ½ inch (12 mm) with a toothpick from the top down.

Take a long, very sharp serrated knife and place it horizontally on the edge of the cake at the level of the top toothpick. The trick is to keep the knife perfectly level, using the toothpick as a guide. Put one hand on top of the cake and slowly spin the cake on the cake stand, keeping the knife level. Let the spinning motion do the work: Don't saw, just maintain light, steady pressure on the knife, so that it slices cleanly through the cake, making an even layer.

Set the first cut layer aside on a cardboard round. Repeat the process to create 2 more layers from the first cake round, so you end up with 3 layers total. Do this with the remaining 3 cake rounds, for a grand total of 12 layers of cake.

Chances are, not all of the layers are perfect. If they are, then you could theoretically make 2 separate cakes (and have 2 layers left over!). But I've got a feeling you're looking at the mess before you and you're thanking St. Valentine that you've got the extra. Choose the best-looking and most even layers of cake: 3 of pomegranate and 3 of key lime. Brush the top of each layer with simple syrup and set one layer of key lime aside on a cake round and cover with plastic wrap.

Place a pomegranate layer on a cardboard cake round and spread about 1 cup of buttercream evenly over the top, about ⅛ inch (3 mm) thick. Place a key lime cake layer on top of the buttercream layer and press gently to adhere. Add another ⅛-inch (3-mm) layer of buttercream to the top. Repeat the process with another pomegranate and then another key lime cake layer, then another  pomegranate. You now have a 5-layer cake sitting in front of you. Phew. The easy part is over. Place this cake in the refrigerator until the buttercream has completely set, about 1 hour.

Take a deep breath. Now take another. Find a 9-inch (23-cm) round cake pan or pot lid. (You need a guide, that's all.) Set it aside. Get a really sharp, thin knife. It can be serrated or not. Dip the knife in scalding-hot water and dry it. Take the cake out of the refrigerator and centre your 9-inch (23-cm) circle guide on top of the cake. Using your knife, trace around the edge of the circle to create a very shallow guideline. Again, this is just a marker, not a deep cut.

Remove your circle guide. Place your knife at an angle of about 45 degrees and cut into the layers, along the outline you made in the cake (see photos 1 and 2). You want to take out a cone-shaped chunk from the middle of the cake. You may feel the knife hit the cardboard round at the bottom-that's okay. Just keep the knife steady and even as you cut at an angle into the cake. When you've gotten all the way around, take another cardboard round and place it on top of the cake. Invert the cake and lift it from the sides so that the cone you've cut comes out (see photos 3 and 4). Set the cone of cake aside.

Invert the original cake, now with a crater in the centre, back to its original position. Coat the third and last layer of key lime cake with a ⅛-inch (3-mm) layer of buttercream (see photo 5), then place it on the cratered cake so the coated side sits on top of the rim (see photo 6). Press very gently on the centre of the cake so that you fill the crater with the piece of key lime cake. It may crack a little- that's OK. Keep pressing along the top until you've created an indentation at the middle of the cake that mimics your original crater (see photo 7). (It's scary to be shoving a cake into place, but that's what you need to do.)

Spread a ⅛-inch (3-mm) layer of buttercream into the crater and along the rim (see photo 8). Now grab the cone of cake you set aside and insert it into your newly formed crater. Press gently (see photos 9, 10, and 11). Apply a very thin layer (a crumb coat) of buttercream on the top and sides of the cake (see photo 12) and refrigerate until set.

Preheat the oven to 225°F (107°C).

Take a look around. It's a mess. But chances are you'll have a few cake bits lying around, even some whole layers. Take the pomegranate bits, cut off any browned areas, and place on a sheet pan. Place in the oven for about 20 minutes, until dry. Cool the cake pieces completely, then pulverize them in a food processor to create fine crumbs.

Spread the remaining buttercream on the cake in a smooth, finished layer.

Fold a piece of parchment paper in half and cut out varied sizes of half hearts (so they will be full hearts when you unfold them). Apply the heart stencils to the top and sides of the cake. Pat the cake crumbs evenly onto the areas of exposed buttercream on the top and sides of the cake. Brush any crumbs from the tops of the stencils so that the crumbs don't later tumble into the heart shapes. Gently remove the stencils. Breathe a sigh of relief, and serve.

Bake It Like You Mean It, Published by Stewart Tabori & Chang, Photography by Tina Rupp, £18.99; www.amazon.co.uk