Ingredients

• 1 ¾ cups Organic Unbleached White All-Purpose Flour (219 g)
• ½ tsp Baking Powder
• ½ tsp Kosher Salt
• 1 oz Unsweetened Chocolate (28 g)
• 8 Tbsp unsalted Butter, room temperature (113 g)
• ¾ cup Granulated Sugar (150 g)
• ½ tsp Vanilla Extract
• Egg, room temperature (50 g)

Instructions

1. Weigh flour and sift it into a large bowl. Add baking powder and salt and whisk together.
2. Chop chocolate into small uniform pieces and place it in a small microwave-safe bowl. Microwave in two 30-second bursts, stirring the chocolate after each 30 seconds. Then microwave in 15-second bursts, stirring after each 15-second interval. When there are a couple of pieces left, stir until it’s all melted. Set aside to cool.
3. Place butter and sugar in the bowl of a stand mixer. Mix on medium low speed until the ingredients look creamy. Scrape the bottom of the bowl. Add egg and vanilla extract and beat on medium speed until fully incorporated.
4. Add all the dry ingredients to the batter and mix on low speed until thoroughly combined and the dough starts to form a ball. The dough will weigh about 530 grams.
5. Weigh out 280 grams of dough and put in a small bowl. This dough is your vanilla dough. Add melted chocolate to the dough in the mixer and beat on medium speed until fully incorporated.
6. Tear off four pieces of wax paper, each about 14 inches long. On one piece, place one of the doughs and shape it into a square. Cover it with another piece of wax paper. With a rolling pin, roll the dough through paper to ⅛-inch thick. It should be about 9 x 9 ½-inch square. Trim any dough that exceeds 9 inches and add to the corners so dough is square. Set aside and repeat these steps with the second piece of dough.
7. Stack the two pieces of dough (each still sandwiched between the two pieces of wax paper) on top of a board or baking sheet and refrigerate for 20 minutes. The dough is sticky, so it’s only chilled long enough so it’s easier to handle and stack.
8. Remove dough from the refrigerator. Lay vanilla dough on a work surface and remove the top piece of wax paper only. Remove the top layer of wax paper from the chocolate dough and use the other piece of wax paper to invert the chocolate on top of the vanilla dough, lining up the edges as evenly as possible.
9. Use the wax paper under the vanilla dough to help roll the doughs into a cylinder. Trim ends so the cylinder is straight. Wrap dough in the wax paper and twist the ends to close.
10. Chill for 60–90 minutes. Right before the dough is removed from the refrigerator, preheat the oven to 350°F. Line one or two baking sheets with parchment paper.
11. Unwrap the dough and place it on a cutting board. Cut the dough into ¼-inch slices. Place the slices 1 inch apart on the baking sheet. Bake for 10–12 minutes, until the bottom edges of the cookies barely turn a light brown. While the first set of cookies is baking, return the other sliced cookies to the refrigerator.
12. Remove cookies from the oven, let sit on the cookie sheet for about 2 minutes, then use a spatula to remove to a wire cooling rack.
13. If using only one baking sheet, let cool completely before baking the next batch of cookies. If using two baking sheets, put cookies on the second baking sheet and repeat the baking instructions.