Separate two eggs, putting each white in a separate bowl (discard yolks or save for another use); set aside. In a small bowl, beat butter and 3/4 cup sugar until crumbly. Beat in the whole egg, one egg white and vanilla until well combined. Combine flour and cocoa; gradually add to egg mixture until blended. Pour into a 9-in. square baking pan coated with cooking spray; set aside.
In a small bowl, beat cream cheese and remaining sugar until smooth. Beat in the second egg white. Drop by rounded tablespoonfuls over the batter; cut through batter with a knife to swirl.
Bake at 350° for 25-30 minutes or until set and edges pull away from sides of pan. Cool on a wire rack. Yield: 1 dozen.