Preheat oven to 350° with rack in middle of oven. Line a cookie sheet with parchment paper.
TO MAKE THE COOKIE DOUGH: In medium bowl, whisk together All-Purpose Flour Artisan Blend, 3 tablespoons cocoa powder, cream of tartar, baking soda, and salt; set aside.
In bowl of stand mixer, beat together butter and 1¾ cups sugar until fluffy. Add eggs one at a time, beating each until creamy and completely mixed in. Slowly add the flour mixture and mix until well combined.
TO MAKE THE TOPPING: In small deep bowl, whisk together 1/3 cup sugar and 1 tablespoon cocoa powder for topping.
Roll dough into 1-inch balls. Roll each ball in topping to coat it. Place balls on cookie sheet, leaving space for the cookies to spread.
Bake one cookie sheet at a time, about 12 minutes, until center is puffed up and cracking. The cookies will collapse when removed from the oven. The middles, between cracks may look uncooked. Cookies should be crunchy on the outside and a little soft in the middle. Cool for 2 minutes and then add sprinkles if desired.
NOTE: The dough freezes well in an airtight container. Bake thawed cookie dough at 350° for 1-2 minutes longer than as directed above, or until done.