Preheat oven to 350°F (180°C). Place graham crackers into a large resealable plastic bag. Finely crush into crumbs using Baker's Roller®;. Combine graham cracker crumbs, powdered sugar and butter in Small Batter Bowl. Using Small Scoop, place scant scoop of crumb mixture in each cup of Deluxe Mini-Muffin Pan. Press crumbs to form shallow cups with Mini-Tart Shaper. Bake 4-5 minutes or until edges are bubbling. Meanwhile, break two of the candy bars into rectangles. Remove pan from oven; place one rectangle into each cup.
Cut marshmallows in half crosswise using Professional Shears dipped in cold water. Place one marshmallow half, cut-side down, into each cup. Return to oven 1-2 minutes or until marshmallows are just slightly softened. Remove from oven to Stackable Cooling Rack; cool 15 minutes. Carefully remove cups from pan. Cool completely.
Break remaining candy bars and place in (1-cup/250 mL) Prep Bowl. Microwave on HIGH 1 minute-1 1/2 minutes or until melted and smooth, stirring every 20 seconds. Dip the top of each marshmallow in melted chocolate. Turn top-side up and let stand 40 minutes-1 hour or until set.