Preheat oven to 350°F. Microwave chocolate and butter in large microwavable bowl on HIGH 2 min. or until butter is melted. Stir until chocolate is completely melted. Stir in sugar. Blend in eggs and vanilla. Add flour; mix well. Spread into greased 12-inch pizza pan.

Bake 25 to 30 min. or until toothpick inserted in center comes out with fudgy crumbs. DO NOT OVERBAKE. Cool in pan on wire rack.

Add milk to dry pudding mix. Beat with wire whisk 2 min. or until well blended; spread over brownie, leaving a 1-inch border around edge. Sprinkle with crushed cookies to resemble dirt. Cut into 16 wedges to serve. Decorate with Easy Marshmallow Snails as desired.