Heat oven to 350°F. Grease and flour 24 large (2 3/4x1 1/4-inch) muffin cups (dark or nonstick pans not recommended). In large bowl, beat cake mix, pudding mix, water, oil and eggs with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl constantly. Place 1/4 cup batter in each muffin cup. Spoon 1 tablespoon cold chocolate mixture on top of batter in center of each cup.