Spread softened ice cream evenly into two wax paper-lined, 8" round cakepans; cover and freeze until ice cream is firm.
Slice cookie dough into 16 (1/2"-thick) slices. Place 3" apart on lightly greased cookie sheets.
Flatten each cookie to a 2" circle. Bake at 350° for 8 minutes. (Cookies will spread during baking.) Cool on cookie sheets 1 minute. Remove to wire racks, and cool completely. Spread 1 teaspoon fudge topping on bottom of each cookie.
Remove ice cream from pans, working quickly with one pan at a time; peel off wax paper. Cut ice cream into 3" circles, using a 3" biscuit cutter. Place each ice cream circle between 2 cookies, fudge sides in; press gently. Place sandwiches in freezer on a cookie sheet. Cover and freeze 30 minutes.
Roll sides of each ice cream sandwich in crushed peppermint candy or decorator sprinkles. Serve sandwiches immediately, or wrap each sandwich in plastic wrap and freeze.