Heat oven to 350ºF. In large bowl, beat 1/4 cup butter and the cream cheese with electric mixer on medium speed, or mix with spoon. Stir in flour, 1/4 cup powdered sugar, 2 tablespoons cocoa and the vanilla. Divide dough into 24 equal pieces. Press each piece in bottom and up side of small muffin cup, 1 3/4x1 inch, ungreased or lined with foil or paper baking cups.