Preheat oven to 350°. In a large bowl, beat the eggs, butter and vanilla until smooth. Whisk together the dry ingredients; gradually add to egg mixture. Stir in chocolate chips. Set aside 1 cup for topping. Spread remaining batter into a greased 13x9-in. baking pan. , For the filling, in a small bowl, beat the cream cheese, peanut butter and sugar until smooth. Beat in egg and milk on low just until combined. Carefully spread over batter. Drop reserved batter by tablespoonfuls over filling. Cut through batter with a knife to swirl. , Bake until a toothpick inserted in the center comes out clean, 35-40 minutes (do not overbake). Cool completely on a wire rack. Chill until serving.