Combine muffin packet, butter and 1 egg: stir to blend. Press half the mixture in a greased 8x8 baking pan. Beat cream cheese, sugar, egg yolk and vanilla until smooth, pour over crust. Crumble remaining muffin dough evenly over cream cheese mixture; sprinkle half of cinnamon and sugar packet over top, reserving remaining cinnamon and sugar for future use. Bake at 375° for 20-25 minutes; cool completely. Makes 16 servings