Mini Chocolate Cakewiches

INGREDIENTS

• 1/2 teaspoon vanilla extract
• Vegetable oil cooking spray
• 1/2 cup skim milk, divided
• 1/2 cup nonfat plain Greek yogurt
• 1/2 cup granulated sugar
• 1 egg white
• 1/2 teaspoon baking soda
• 2 tablespoons confectioners' sugar
• 3 tablespoons unsalted butter
• 1/4 cup unsweetened cocoa powder, plus more for dusting
• 3/4 cup unbleached all-purpose flour
• 1/2 cup reduced-fat cream cheese, at room temperature