Beat butter and sugar on medium speed until light and fluffy, about 3 minutes. Scrape down the bowl. Beat in eggs one at a time, then almond extract. The mixture should look pale and creamy.

Whisk together flour, baking powder, and salt. Reduce mixer to low and add flour mixture in two batches, mixing just until no dry streaks remain. Do not overmix.

Divide dough into three equal portions (about 12 oz each). Leave one plain. Mix cocoa powder into second portion until uniform and chocolate-colored. Mix strawberry jam (and food coloring if using) into third portion until evenly pink.

Shape each dough portion into a 10-by-2-inch rectangle, about 1/2 inch thick. The easiest method: press dough into a lightly floured 10-inch loaf pan lined with plastic, then lift out and square the edges. Wrap each rectangle tightly in plastic and chill 45 minutes until firm.

Unwrap doughs. Brush vanilla rectangle lightly with egg white. Press chocolate rectangle on top, aligning edges. Brush chocolate layer with egg white, then press strawberry layer on top. Trim edges for clean sides. Wrap and chill 30 minutes more until solid.

Preheat oven to 350F. Line baking sheets with parchment. Using a sharp knife, slice the dough block crosswise into 1/4-inch thick cookies. You should get about 36. Place 1 inch apart on sheets.

Bake 10-12 minutes until edges are just set and bottoms are pale golden. Centers will look slightly underdone - they firm up as they cool. Cool on sheets 5 minutes, then transfer to wire racks.