Place frozen biscuits on microwavable plate. Microwave uncovered on High 15 seconds; turn over, and microwave about 10 seconds longer or until biscuits are softened. Spray work surface lightly with cooking spray. On surface, press each biscuit into 5-inch round. Place 1 biscuit on outside bottom surface of each custard cup. Gently press and stretch dough about two-thirds of the way down side of each cup.