Let ice cream stand at room temperature 30 minutes, or microwave it in 10-second intervals until spreadable.
STEP 1 Coarsely chop 6 cookies; set aside.
STEP 2 Make crust: Process 10 cookies in a food processor until fine crumbs form. Add butter, and process until combined. Transfer to a 9-inch tart pan with a removable bottom. Using the bottom of a measuring cup or glass, press crust firmly into pan. Top with a circle of 8 cookies.
STEP 3 Dollop ice cream by the cup all over crust. Using a rubber spatula, gently spread. Sprinkle edge of ice cream with chopped cookies, forming a border. Freeze until firm, at least 4 hours, or cover with plastic wrap and freeze, up to 1 week.
STEP 4 To unmould, run a warm, damp cloth or sponge around outside edge of pan. Lift removable bottom with tart out of pan. Transfer to a serving plate, and cut into slices.