HEAT oven to 350°F.
BEAT cake mix, dry pudding mix, eggs, sour cream, oil and water in large bowl with mixer until blended. Chop 4 oz. chocolate. Stir into batter along with 1/2 cup chopped cookies. Spoon into 30 paper-lined muffin cups.
BAKE 20 to 23 min. or until toothpick inserted in centers comes out clean. Cool in pans 10 min.; remove to wire racks. Cool completely.
COMBINE COOL WHIP and remaining chopped cookies; frost cupcakes. Melt remaining chocolate as directed on package; drizzle over cupcakes.