Stir together peanut butter, eggs, and vanilla in large bowl.
Stir in brown sugar until combined. Add baking mix and 3/4 cup dark chocolate morsels, stirring just until moistened. Spread mixture in a lightly greased 15- x 10-inch jelly-roll pan.
Bake at 325° for 20 minutes or until golden brown. Remove from oven, and sprinkle evenly with remaining 1 1/4 cups dark chocolate morsels; let stand 5 minutes or until chocolate melts. Spread melted chocolate evenly over top. Cut into triangles, bars, or squares.
Note: For testing purposes only, we used Bisquick All-Purpose Baking Mix and Hershey's Special Dark Chips.