Chocolate Peppermint Pinwheel Cookies - Alton Brown

Ingredients

• 3 cups all-purpose flour
• 3/4 teaspoon baking powder
• 1/4 teaspoon kosher salt
• 16 tablespoons (2 sticks) unsalted butter, at room temperature
• 1 cup sugar
• 1 large egg, beaten, plus 1 large egg yolk, divided
• 1 tablespoon whole milk
• 3 ounces unsweetened chocolate, melted
• 1 teaspoon vanilla extract
• 1 teaspoon peppermint extract
• 1/2 cup crushed candy canes or peppermint candies
• powdered sugar, for rolling dough