Preheat oven to 350 degrees F. Line 8" square baking pan with nonstick foil. (If using regular foil - use cooking spray.) Beat all crust ingredients in a large bowl at medium speed 1 - 2 minutes or until fine crumbs form; press into bottom of pan. Bake 12 - 15 minutes or until golden brown. Cool completely on wire rack.
Unwrap caramels. Heat caramels & water in medium heatproof bowl set over saucepan of simmering water 8 - 10 minutes or until melted (bowl should not touch water), stirring occasionally. Remove from heat; keep warm.
Meanwhile, beat 1 C of the powered sugar & marshmallow cream in a standing mixer at low speed until combined. Sprinkle remaining 2 Tbsp powered sugar over flexible cutting board or sheet of parchment paper. Lightly coat hands with powdered sugar; gently pat out marshmallow mixture on board or paper into 8" square. Brush off excess powdered sugar.
Spread 1/2 C of the melted caramel over crust; sprinkle with 1 C of the peanuts. Top with marshmallow square by turning cutting board or paper with marshmallow mixture upside-down over peanuts, pressing down firmly to adhere layers. Reserve 2 Tbsp of the caramel; pour remaining caramel over marshmallow layer. Top with remaining 1 C peanuts & candy corn, patting down firmly.
Reheat reserved caramel; drizzle over bars. Refrigerate 30 minutes or until set.
Lift foil to remove bars from pan; remove foil. Cut into 24 bars. Cover & store in refrigerator & enjoy!