1 (18 1/4 or 18 1/2 oz.) pkg. white cake mix
1 (14 oz.) can sweetened condensed milk (not evaporated)
2/3 c. chocolate flavored syrup
2 c. (1 pt.) whipping cream (heavy), whipped (do not use non-dairy whipped topping)
1 (8 oz.) container frozen non-dairy whipped topping, thawed
Additional chocolate flavored syrup

Prepare and bake cake mix as directed for 13x9 cake. Cool slightly. Turn out on a sheet of foil. Cool thoroughly; set aside. In large mixing bowl combine sweetened condensed milk, 2/3 cup syrup. Fold in whipped cream.

Line 13x9 inch baking pan with foil, extending foil above sides of pan. Pour chocolate mixture into prepared pan; cover. Freeze 6 hours or until firm. Lift ice cream out of pan with foil; turn out evenly on top of cake layer.

Trim ice cream to fit cake layer. Quickly frost with whipped topping and drizzle with chocolate syrup. Freeze. Can be made 2 weeks ahead.