Preheat the oven to 350°F. Spray 3 quarter-size sheet pans (~9x12 inches) with non-stick baking spray and line with parchment paper. Set aside.

In a large mixing bowl, beat together butter and almond paste until smooth (some small bits of almond paste may remain, but try to break them down as much as possible to combine with the butter.)

Add cake mix, eggs, milk, and almond extract to the bowl. Using an electric mixer, beat on medium speed for 2 minutes, or until the batter is well combined and fluffy.

Separate the batter into three bowls (about 3 ⅓ cups of batter per bowl).

Color each batter with food coloring to make green batter, yellow batter, and pink batter.

Transfer each bowl of batter to a separate sheet pan. Use an offset spatula to spread into an even layer. Place pans in the oven and bake for about 15 minutes, until the cakes are cooked through and a toothpick inserted in the center comes out clean, or with just a few moist crumbs. Halfway through baking time, rotate the pans for even baking.

Remove pans from the oven and transfer to cooling racks. Allow the cakes to cool completely in the pans.

Wrap the three layers and bottom pan tightly in plastic wrap. Next, place one of the empty sheet pans back on top of the wrapped cake. Place a heavy cast iron skillet or several canned goods on top of the pan to weigh it down. (This will compress the layers together.) Transfer this “package” to the refrigerator to chill for at least 4 hours, or overnight.

Remove the cake from the refrigerator, and remove the weights, the top pan, and the plastic wrap.

Place a fresh sheet of parchment paper over a large cutting board and turn the full cake out onto the cutting board so that the green layer is on top. Remove the parchment from the green cake layer.

In the top of a double boiler (or in the microwave), melt the chocolate chips and the shortening together until fully melted and smooth.

Pour half of the melted chocolate onto the green cake “top” and use a large offset spatula to spread it smoothly to cover the top of the cake.

Place the cake into the refrigerator and chill for 15 minutes, or until chocolate is set.

Flip the whole cake over and repeat spreading the remaining melted chocolate over the top of the cake (the pink layer). You can make swirls or decorations in the chocolate if you wish.

Chill until the top layer of chocolate is set.

Slice straight down each side to form four straight edges to the cake. Cut into pieces and serve.