Elf‘s Mini S’mores Cheesecakes

INGREDIENTS
1 cup graham cracker crumbs
1/4 cup unsalted butter, melted
2 (8 oz.) packages cream cheese, at room temperature
1 3/4 cups granulated sugar, divided
1/2 cup cocoa powder
3 large eggs
4 egg whites, at room temperature
1/4 cup sour cream, at room temperature
2 tsp. vanilla extract, divided
1/2 tsp. cream of tartar