We used Nilla wafers, French butter cookies, and Famous chocolate wafers: Let ice cream or sorbet soften at room temperature for 15 to 20 minutes, then place a small scoop on the flat side of a cookie. Top with another, and press gently. If desired, roll the sides of the sandwich through rainbow or chocolate sprinkles to coat the ice cream. Freeze on a baking sheet for 1 hour to harden; wrap each sandwich in plastic. They will keep, frozen, for about a week.