20 squares graham crackers, divided
3/4 cup (1 1/2 sticks) butter or margarine
4 (1 ounce) squares unsweetened baking chocolate
2 cups granulated sugar
1 teaspoon vanilla extract
1 cup all-purpose flour
1 (10 1/2 ounce) package miniature marshmallows
1 (12 ounce) package semisweet chocolate chunks
Heat oven to 350 degrees F. Line a 13 x 9-inch baking pan with foil; grease foil. Place 15 of the graham squares in bottom of pan, overlapping slightly.
Microwave butter and chocolate in large microwavable bowl on high 2 minutes or until butter is melted. Stir until chocolate is completely melted.
Stir sugar into chocolate mixture until well blended. Mix in eggs and vanilla extract. Stir in flour until well blended. Spread over graham squares in pan.
Bake 30 to 32 minutes or until a wooden pick inserted in center comes out with fudgy crumbs. Do not overbake. Sprinkle marshmallows and chocolate chunks evenly over top. Return to oven 5 to 7 minutes or just until marshmallows are golden.
Press remaining 5 graham squares, broken into large pieces, into top of brownie. Cool in pan on wire rack. Lift out of pan onto cutting board. Cut into bars.
Tip: For ease in cutting, dip knife in warm water and wipe dry between cuts.