1. Heat oven to 350°F.(325°F. for glass baking dish). Remove wrappers from peppermint patties. Grease 13x9x2-inch baking pan.
2. Stir together butter, sugar and vanilla in large bowl. Add eggs; beat until well blended. Stir in flour, cocoa, baking powder and salt; blend well. Reserve 2 cups batter. Spread remaining batter in prepared pan. Arrange peppermint patties about 1/2 inch apart in single layer over batter. Spread reserved 2 cups batter over patties.
3. Bake 50 to 55 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack; cut into squares. Makes 24 to 36 brownies.