Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups. Make and bake cake mix as directed on box for 24 cupcakes. Cool in pans 10 minutes. Remove from pans to cooling racks. Cool completely, about 30 minutes.
By slowly spinning end of round handle of wooden spoon back and forth, make deep, 3/4-inch-wide indentation in center of top of each cupcake, not quite to bottom (wiggle end of spoon in cupcake to make opening large enough).
In medium bowl, stir together filling ingredients. Spoon into small resealable food-storage plastic bag; seal bag. Cut 3/8-inch tip off 1 bottom corner of bag. Insert tip of bag into opening in each cupcake; squeeze bag to fill opening.
Frost cupcakes. Garnish each with about 2 teaspoons broken cookies. Store loosely covered.