In large bowl, beat cake mix, champagne, egg whites and oil with electric mixer on low speed 30 seconds. Scrape bowl. Increase speed to medium and beat 2 minutes. Divide batter evenly among baking cups, filling about 1/2 full. Bake 18-20 minutes or until a toothpick inserted in the center comes out clean. Let cool in pan on cooling grid 10 minutes; remove and let cool completely.