Step 1

Drop six 1/2-cup mounds of ice cream onto waxed paperulined baking sheet. Using metal spatula, shape each mound into 3- to 3 1/2-inch square. Freeze squares while preparing dough.

Step 2

In large bowl, beat butter and sugar using electric mixer until smooth. Beat in egg yolk and vanilla. In medium bowl, mix flour, cocoa and salt. Add to butter mixture and beat until soft dough forms. Gather dough into ball; flatten into rectangle. Roll out dough between 2 sheets of waxed paper to 13- by 10-inch rectangle. Place dough, still between waxed paper sheets, on baking sheet. Chill until firm, at least 1 hour and up to 1 day.

Step 3

Preheat oven to 300 degrees. Line large baking sheet with parchment paper. Peel top sheet of waxed paper off dough; discard. Trim dough to 12- by 9-inch rectangle; then cut dough into twelve 3-inch squares. Transfer squares to parchment-lined baking sheet, discarding waxed paper and spacing them about 1 inch apart. Bake until cookies are firm, about 20 minutes. Cool cookies completely on baking sheet.

Step 4

Arrange 6 cookies, flat-side up, on work surface. Top each with frozen ice cream square, then another cookie, flat-side down, pressing slightly to adhere. Cover and freeze sandwiches until ready to serve. Ice cream sandwiches can be made up to 4 days ahead. Store, wrapped in plastic, in the freezer.

Step 5

This recipe yields 6 servings.

Step 6

Comments: We call for coffee ice cream in these frozen sandwiches, but you can use any flavor you'd like.