Zebra-Striped Shortbread Cookies | The Fancy Pants Kitchen

Ingredients

• 2 & 1/3 cups all-purpose flour, divided
• 1 & 1/2 tsp kosher salt, divided
• 1/3 cup Dutch-process cocoa powder
• 1 & 1/4 cups (2 & 1/2 sticks) unsalted butter, room temperature
• 2/3 cup granulated sugar
• 1/4 cup powdered sugar
• 1 large egg yolk
• 1 tsp vanilla extract or paste
• 1 large egg, beaten to blend
• 1/4 cup sanding sugar (any color)