Preheat oven to 350°F. Line a 9x13 inch baking dish with parchment paper.

Beat whites in a mixer fitted with whisk attachment at medium-high speed until they just hold stiff peaks.

Add ¼ cup sugar a little at a time, beating at high speed until whites hold stiff, slightly glossy peaks. Transfer to another bowl.

Switch to paddle attachment, then beat together almond paste and remaining ¾ cup sugar until well blended, about 3 minutes.

Add butter and beat until pale and fluffy, about 3 minutes.

Add yolks and almond extract and beat until combined well, about 2 minutes.

Reduce speed to low, then add flour and salt and mix until just combined.

Fold half of egg white mixture into almond mixture to lighten, then fold in remaining whites gently.

Divide batter into 3 bowls. Stir food coloring into each bowl. Pour 1st colored batter into prepared pan and spread evenly with an offset spatula (layer will be about ¼ inch thick).

Bake each layer 8 to 10 minutes, until just set. (It is important to undercook.Tops will look still somewhat glossy.)

Transfer to a rack to cool. Reline the baking dish with parchment and cook the next layer, followed by the last layer.

When all layers are cool, invert 1 layer onto a wax-paper-lined large baking sheet. Discard paper from layer and spread with half of preserves. Invert next on top of 1st layer, discarding paper. Spread with remaining preserves. Invert final layer on top of previous layer and discard wax paper.

Cover the top layer with plastic wrap and top it with another pan or baking dish. Add cans from your pantry to weigh it down to compress the layers. Chill at least 8 hours.

Remove weight and plastic wrap.

Trim edges of assembled layers with a long serrated knife.

In a microwave safe bowl, melt the chocolate discs for 1 minute. Let sit for 30 seconds then stir until smooth. If still not smooth, reheat for 15 second intervals.

Quickly spread half of the chocolate in a thin layer on top of the cake and smooth out with an offset spatula.

Chill, uncovered, until chocolate is firm, about 10 minutes.

Cover with another sheet of wax paper and place another baking sheet on top, then invert cake onto sheet and remove paper.

Reheat chocolate for 30 seconds, or until smooth, then quickly spread with remaining chocolate. Chill until firm, about 30 minutes.

Cut lengthwise into 4 strips. Cut strips crosswise into ¾-inch-wide cookies.