Step 1

Beat dry cake mix, COOL WHIP, egg whites and 1-1/2 cups coconut in large bowl with mixer until blended. Refrigerate 2 hours.

Step 2

Heat oven to 375°F. Roll dough into 84 balls, using 1 tsp. dough for each. Place, 1 inch apart, on parchment-covered baking sheets. Spray bottom of drinking glass with cooking spray. Dip in granulated sugar, then use to flatten each ball to 1-1/2-inch diameter.

Step 3

Bake 5 min. or just until edges of cookies are firm. (Do not overbake.) Cool on baking sheet 2 min. Remove to wire racks; cool completely.

Step 4

Beat butter and milk in medium bowl until creamy. Gradually beat in powdered sugar until blended. Stir in remaining coconut.

Step 5

Fill cookies with coconut mixture to make 42 sandwiches, adding about 1 tsp. coconut mixture to each sandwich.