This is a basic icebox sugar cookie, but adding chocolate to half and using a quick little stacking trick, you get the checkerboard effect with no heavy lifting or heavier thinking.
Two sticks of butter (1 cup, half a pound) (softened)
¾ cup baker’s or granulated sugar
½ cup powdered sugar
½ tsp salt
2 egg yolks
2 tsp vanilla
2¼ cups all-purpose flour
2 Tbs dutch-process cocoa
1 oz semisweet chocolate (melted, then cooled)
3-4 Tbs crushed peppermint sticks (optional)
What You Do:
Beat the butter, both sugars, and salt with either the paddle attachment of a stand mixer or a regular electric mixer — around 3 minutes on medium speed, until it’s 100% incorporated and fluffy. Add the egg yolks and vanilla and give it another minute. Add the flour a half-cup at a time and mix on slow. Then divide the dough into two halves.
With the second half, mix in the two chocolates.
Place a large square of wax paper on the counter and scrape out the dough in the center of the paper. Gently shape the dough into a rectangular bar, around 10 inches long, 1 inch high, and 2 inches wide, and then fold the paper around the dough and form it into as smooth and squared-off as you can. Repeat with the second half of the dough.
Wrap both bars in plastic wrap (you can leave it in the wax paper) and refrigerate for about an hour, maybe two, until it’s firm. Then unwrap the bars and slice them long-ways, resulting in two vanilla sticks and two chocolate sticks, both 10″ x 1″ x 1″.
Place one vanilla stick next side-by-side with a chocolate stick. Then place the other vanilla stick on top of the chocolate stick, and the other chocolate on top of the vanilla. (Geometry! Yay!)
Re-wrap them in wax paper and give them a gentle squeeze to form one large 2″ x 2″ bar. Then re-wrap with plastic wrap and return to the fridge.
Slice off quarter inch squares from the end of your dough bar, and place them one-half to one inch apart on the cookie sheets. Bake for 12-14 minutes, just until the edges start to very lightly brown. Remove from the oven, cool on the sheet for 5 minutes, then complete cooling on a wire rack.