Heat oven to 350°. Generously grease bottom, sides and rim of two 9-inch pie pans. In a large bowl, blend dry cake mix, frosting, water and oil together at low speed until moistened. Beat 2 minutes at highest speed. Spread half the batter in the bottom of each pan. Do not spread up sides of pan! Bake at 350° for 25 to 30 minutes. DO NOT OVERBAKE. Cakes will collapse to form shells (sometimes I purposefully drop the pie pans from 3-4" height above the counter to make them fall). Cool completely.
Spread softened ice cream in shells, leaving a ½" rim. If desired, heat remaining frosting just until softened. Drizzle over ice cream and swirl with knife. Store in freezer.
Note: Any flavor of ice cream will work -- from plain vanilla to Jamocha Almond Fudge. Be creative!