Step 1

Whisk together the flour, baking powder, and salt.

Step 2

In a medium-sized bowl cream together the butter and sugar with a hand mixer on medium speed until light and fluffy. About 5 minutes.

Step 3

Add the egg, egg yolk, and vanilla; beat until combined.

Step 4

Add the flour mixture; beat just until combined.

Step 5

Divide the dough into 3 equal parts; set aside one portion of dough.

Step 6

Stir preserves, strawberry extract, and desired amount of food color gel into one dough portion until combined.

Step 7

Stir cocoa and chocolate into the remaining dough portion until combined.

Step 8

Fit a 9X5-inch loaf pan with a parchment sling.

Step 9

Press chocolate dough into the bottom of the pan, followed by the vanilla dough, then the strawberry dough.

Step 10

Cover the pan with plastic wrap; chill for 3 hours or overnight. You may also freeze for 1 hour.

Step 11

Preheat oven to 350 °F. Line baking sheets with parchment.

Step 12

Remove the dough loaf from pan; cut into ¼-inch-thick slices. Place slices on prepared baking sheets; sprinkle with sparkling sugar.

Step 13

Bake cookies until edges are set, 11-12 minutes. Let cookies cool on baking sheets 2 minutes, then transfer to a rack to cool completely.