Preheat the oven to 350°F and butter the 9×13-inch rectangular sheet pan. Then line with wax paper, making sure to leave an overhang of 2” of paper on each side, which will help to pull the cake out later. Butter the wax paper.
Beat egg whites in a mixer with the whisk attachment at medium-high speed until stiff peaks form. (You can also opt to mix by hand with a whisk, though it will take longer). On high speed, slowly pour in ¼ cup of sugar until you have high and glossy peaks. Transfer egg white whip to a bowl.
Switch your mixer to the paddle attachment and on medium-high speed, combine remaining sugar and almond paste (about 3 minutes). Add 4 oz of butter. Mix until smooth and homogeneous. Add the remaining 8 oz of butter and mix again until lump-free (about 3 minutes).
Add in egg yolks, milk, vanilla, and almond extract. Mix until well combined.
Reduce to low speed, gradually add in the flour and salt. Mix to combine and obtain a lump-free mixture.
With a spatula, gently fold the egg white mixture into the almond cake mix. Continue until thoroughly combined.
Divide the batter into 3 bowls.
Stir red food coloring into one batter and the green one in another, adjusting the amount of coloring as needed. The third batter will remain yellow as it is.
Set yellow cake bowl aside, and place the green cake bowl in the fridge covered.
Pour the red cake batter into the sheet pan. (You can also spread it around with an offset spatula or fork, if needed).
Bake the red cake until it‘s set (no longer shiny and slightly brown edges), about 10 minutes. Making sure not to overcook the cake.
Carefully remove the cake from the pan (using the wax paper overhang) and place on a cooling rack, keeping wax paper intact.
Wash the pan and prepare it again as we did in step #1.
Before we bake the yellow cake pan, take the green cake bowl out of the fridge to bring to room temp. Bake the yellow layer as we did with the red. After placing the yellow layer on a cooling rack. Repeat all of the steps again for the green layer.
Line a large baking sheet with wax paper.
When all the layers are cool (about 15 minutes), use the wax paper to flip the green cake face-down on the wax-lined baking sheet. Gently remove the wax paper that’s on top.
Spread half of the preserve thinly over the green cake.
Use the wax paper to flip the yellow cake face-down on the wax-lined baking sheet. Gently remove the wax paper that’s on top.
Spread the remaining preserve thinly over the yellow cake.
Use the wax paper to flip the red cake face-down on the wax-lined baking sheet. Gently remove the wax paper that’s on top
Cover the cake tightly with plastic wrap. Place a baking sheet on top of the cake and put some weight onto it.
Refrigerate for 8+ hours.
After done refrigerating, unwrap the cake and remove the weight. Bring cake to room temp.
Using a serrated knife, trim all the edges of the cake.
Melt the chocolate using a double boiler pot. (If you don’t have a double boiler, you can also melt in the microwave). Add in heavy cream.
Using the offset spatula, quickly spread half of the melted chocolate over the top of the cake.
Refrigerate uncovered for half an hour.
Flip the cake by placing a piece of wax paper on top, and then using a baking sheet on top of that, to control the flipping of the cake.
Spread the remaining chocolate mix over it.
Refrigerate for an additional hour.
Cut the cake into rectangles (we like 12 rectangles when you cut the sheet 4×3, but they will also work as squares). To have clean edges, use a sharp knife that has ran under hot water, making sure to wipe in between each slice made.
Serve and enjoy.