heat oven to 350°F

stir together butter, sugar, and vanilla in a large bowl. add eggs; beat yntil 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 inches apart in a single layer over the batter

spread reserve 2 cups over patties

bake for 50 to 55 minutes or until brownies begin to pull away from sides of pan

cool completely in pan or on a wire rack; cut into squares