Heat oven to 350. Spray an 8x8 cake pan with bakers joy or else grease and flour it well. If you have more than one 8x8 pan use up to 3 to make baking easier since you will bake each layer separately. I use one pan and just bake each layer one at a time.
In a stand mixer with paddle attachment, beat the butter, almond paste, extract and sugar until light and fluffy and well mixed. There will still be some small lumps of almond paste and that is fine.
Reduce the mixer to medium and add the eggs one at a time, letting one mix in before adding the next. Add in the salt and mix again. Then add the flour and mix on low just until combined. Stop and hand mix to make sure it is all well mixed.
Divide the batter into 3 equal portions. I use a scale for this. If you don't have a scale, it should be about 1 cup of batter per bowl. Color the different batters at you'd like.
Pour one bowl of batter into the pan and smooth the top with an offset spatula. Bake for about 10 minutes until the center is set and a toothpick comes out clean.
Cool for 10 minutes on a cooling rack, then flip the pan quickly to get the cake out in one piece. Cool the rest of the way. Repeat with the other cake mixes.
Stack the layers of cake, spreading 1/2 of the apricot jam between each layer. Place in the fridge covered with plastic wrap for at least 1 hour. Remove from the fridge and trim the edges of the cake so that they are nice and even and square.
Melt chocolate in the microwave in 20 second intervals, stirring between each, until smooth. Spread on the top of the cake with an offset spatula. Place back into the fridge until the chocolate is set.
Using a knife heated under hot water and wiped dry, slowly score the chocolate on top of the cake in a 4x4 grid. This is so that the chocolate doesn't break into pieces when you cut it. Using a hot knife, cut the scored lines into 16 cookies.
Store these in the fridge in an airtight container.