Ingredients

• 1/2 cup unsalted butter softened (1 stick)
• 1/3 cup Granulated Sugar
• 1/4 cup Powdered Sugar
• 1 large Egg Yolk
• 1 tsp Vanilla Extract
• 1 cup Unbleached White All-Purpose Flour + 2 Tbsp
• 1/4 tsp Salt

• 1/2 cup unsalted butter softened (1 stick)
• 1/3 cup Granulated Sugar
• 1/4 cup Powdered Sugar
• 1 large Egg Yolk
• 1 oz Dark Chocolate melted and cooled
• 1 tsp Vanilla Extract
• 1 cup Unbleached White All-Purpose Flour
• 2 Tbsp Dutch-processed cocoa powder
• 1/4 tsp Salt

Instructions

1. Begin with the vanilla dough. In a large bowl, cream together the butter and both sugars until light and fluffy, about 3-5 minutes. Beat in the egg yolk and vanilla extract until fully combined. Add the flour and salt and mix until just combined. Place the dough in a bowl or on a clean counter while you prepare the chocolate dough.
2. In a large bowl, cream together the butter and both sugars until light and fluffy, about 3-5 minutes. Beat in the egg yolk, cooled chocolate, and vanilla extract until fully combined. Add the flour, cocoa powder and salt and mix until just combined. Place the dough in a separate bowl. Cover in plastic wrap and refrigerate until firm, about 1-2 hours.
3. Once the dough has firmed up, use your fingers to roll about 2 tablespoons of vanilla dough into a a long snake about 8" long. It helps to do this on a flat, non-stick surface. Repeat until you have three rolls of vanilla dough and three rolls of chocolate. Combine the smaller rolls into one big roll and twist together carefully - you don’t want to break the dough.
4. You should have a thick, twisted log of dough at this point. Roll the dough gently to flatten out the sides, being careful not to make the log too thin - it should be about 2” diameter. Wrap the log in plastic wrap and store in the refrigerator for at least one hour or up to 2 weeks. Repeat with the remaining dough until all has been used.
5. Preheat oven to 325°F and line a large baking sheet with parchment paper. Slice cookies ¼” thick and place 1 inch apart on baking sheet. Bake for 12-15 minutes or until lightly browned around the edges.