Mud Pie Ice Cream Sandwiches

Ingredients

 * 2 pints coffee ice cream, softened slightly
 * 3/4 cup (1 1?2 sticks) unsalted butter, room temperature
 * 1/2 cup plus 2 tablespoons Sugar
 * 1 large egg yolk
 * 1 tsp. vanilla extract
 * 1 1?4 cups all-purpose flour
 * 1/4 cup Dutch-processed cocoa powder
 * 1/4 tsp. salt

Directions

 * 1) Drop six 1?2-cup mounds of ice cream onto waxed paper–lined baking sheet.
 * 2) Using metal spatula, shape each mound into 3- to 3 1?2-inch square. Freeze squares while preparing dough.
 * 3) In large bowl, beat butter and Sugar using electric mixer until smooth.
 * 4) Beat in egg yolk and vanilla. In medium bowl, mix flour, cocoa and salt.
 * 5) Add to butter mixture and beat until soft dough forms. Gather dough into ball; flatten into rectangle.
 * 6) Roll out dough between 2 sheets of waxed paper to 13 x 10-inch rectangle.
 * 7) Place dough, still between waxed paper sheets, on baking sheet.
 * 8) Chill until firm, at least 1 hour and up to 1 day.
 * 9) Preheat oven to 300 °F. Line large baking sheet with parchment paper.
 * 10) Peel top sheet of waxed paper off dough; discard.
 * 11) Trim dough to 12 x 9-inch rectangle; then cut dough into twelve 3-inch squares.
 * 12) Transfer squares to parchment-lined baking sheet, discarding waxed paper and spacing them about 1 inch apart.
 * 13) Bake until cookies are firm, about 20 minutes. Cool cookies completely on baking sheet.
 * 14) Arrange 6 cookies, flat side up, on work surface.
 * 15) Top each with frozen ice cream square, then another cookie, flat side down, pressing slightly to adhere.
 * 16) Cover and freeze sandwiches until ready to serve. ice cream sandwiches can be made up to 4 days ahead.
 * 17) Store, wrapped in plastic, in the freezer.