Double Chocolate Chocolate Chip Cookies

Ingredients (10)

• 1 1/2 cups butter
• 2 cups packed dark brown sugar
• 1 cup granulated sugar
• 2 large eggs + 2 egg yolks
• 4 tsp.  vanilla
• 4 cups all purpose flour
• 1/2 cup cocoa powder
• 1 tsp.  baking soda
• 1 tsp.  salt
• 2 cups semi-sweet chocolate chips