Checkerboard Cookies

Combine the sugars, salt, and 1 1/2 cups (195 grams) of the flour in a food processor. Add cold, diced butter and mix until it disappears, then keep running the machine until it just begins to clump.

Add egg yolk (save the egg white for later) and vanilla and pulse until combined, forming one large or a few smaller smooth masses.

Divide dough in half. Add 1/4 cup (35 grams) remaining flour to one half and mix until just combined to make vanilla dough. For the other half, add cocoa powder to make chocolate dough.

Roll each dough half between two pieces of parchment paper into approximately 4 to 5×10-inch rectangles that are 1/4-inch thick. Freeze for 10 to 15 minutes until firm.

Stack the chocolate and vanilla dough layers, cut the stack in half the long way and stack again, forming one long striped slab. Freeze again until very firm.

Remove the slab from the freezer and cut it the long way into eight 1/4-inch-wide slices. Arrange the slices into a checkerboard log, flipping two of the slices over for contrasting colors. Freeze until solid.

Preheat oven to 350°F (176°C).

Slice the checkerboarded log into 1/4-inch-thick cookies. Brush with egg white, roll in sanding sugar, and arrange on a baking sheet.

Bake for 10 to 12 minutes, until golden brown underneath. Cool on a rack.