Preheat oven to 350 degrees. Grease an 8-inch square baking pan.
In a medium bowl, blend peanut butter, 3/4 cup sugar, and 1 egg. Press mixture into bottom of pan.
In a mixing bowl, beat butter, 1 cup sugar, 2 eggs, and vanilla until fluffy. Add cocoa and flour; mix on medium speed until smooth. Spread over peanut butter layer.
Bake 35 to 40 minutes, until a tester inserted in the center comes out with a moist crumb.
Recipe submitted by busy-mom on 3/30/00