Chocolate Star Cookies

INGREDIENTS

• 24 Tbs. (3 sticks) unsalted butter, at room temperature
• 3 cups firmly packed light brown sugar
• 3 eggs
• 1 Tbs. vanilla extract
• 3 1/2 cups all-purpose flour
• 1 cup plus 2 Tbs. unsweetened cocoa powder
• 1 1/2 tsp. baking soda
• 1 1/2 tsp. cream of tartar
• 3/4 tsp. salt
• 4 Tbs. coarse sugar, or as needed