Italian Rainbow Cookies
Makes about 60 cookies
Adapted from Smitten Kitchen
4 large eggs, separated
1 cup sugar, divided
8 oz almond paste
2 1/2 sticks (1 1/4 cups) unsalted butter, softened
1 tsp almond extract
2 cups all-purpose flour
1/2 tsp salt
25 drops red food coloring*
25 drops green food coloring*
12 oz apricot preserves, heated and strained
7 oz fine-quality bittersweet chocolate, chopped
*You could also use roasted beet and matcha for natural food coloring
Preheat oven to 350°F. Line a 13- by 9-inch baking pan with parchment paper, and butter the bottom. Leave a 2-inch overhang on opposite ends.
Beat egg whites in mixer fitted with whisk attachment at medium-high speed until they just hold stiff peaks. Continue beating at high speed while adding 1/4 cup sugar a little at a time. Beat until the egg whites hold stiff, slightly glossy peaks. Transfer to another bowl.
Switch the mixer to paddle attachment. Beat almond paste and remaining 3/4 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 but thoroughly.
Divide batter between 3 bowls. Add red food coloring into one of the bowls and stir until combined. Add green food coloring to another bowl, mixing until combined. Leave the third bowl plain. Set the plain batter aside. Cover and chill the green batter. Pour red batter into prepared pan and spread evenly with offset spatula (layer will be about 1/4 inch thick).
Bake red layer 8 to 10 minutes, until just set, and slightly undercooked. It will look like it’s not quite done, but a tester will come out clean.
Using the parchment paper overhang, transfer layer to a rack to cool for about 15 minutes. Clean pan, then line with parchment paper and butter paper in same manner as above. Bake white layer in prepared pan until just set. As white layer bakes, bring green batter to room temperature. Transfer white layer to a rack. Prepare pan as above, then bake green layer in same manner as before. Transfer to a rack to cool. Do not stack the layers as they cool.
When all layers are cool, invert green layer onto a parchment-lined large baking sheet. Discard paper from layer and spread with half of preserves. Invert white on top of green layer, discarding paper. Spread with remaining preserves. Invert red layer on top of white layer and discard paper.
Cover with plastic wrap and weight with a large baking pan. Chill at least 4-8 hours.
Remove weight and plastic wrap. Bring to room temperature. Melt chocolate in a double boiler over of barely simmering water, stirring until smooth. Remove from heat. Keep chocolate over water.
Trim edges of assembled layers with a long serrated knife. Quickly spread half of chocolate in a thin layer on top of cake. Chill, uncovered, until chocolate is firm, about 15 minutes. Cover with another sheet of wax paper and place another baking sheet on top, then invert cake onto sheet and remove paper. Quickly spread with remaining chocolate. Chill until firm, about 30 minutes.
Cut lengthwise into 4 strips. Cut strips crosswise into 3/4-inch-wide cookies. (The cake is easier to cut when frozen).
Cookies can be stored at room temperature in an airtight container up to 2 weeks or may be frozen for longer.