Heat oven to 350°F. Place mini paper baking cup in each of 24 mini muffin cups; lightly spray paper cups with cooking spray.
In medium bowl, mix all ingredients except chocolate chunks with wooden spoon. Spoon batter evenly into muffin cups, filling each about 3/4 full. Lightly press 1 chocolate chunk into batter in each cup.
Bake 16 to 18 minutes or until light golden brown and tops spring back when lightly touched in center.
Cool in pans on cooling racks 1 minute. Remove from pans to cooling racks; cool 5 minutes before serving.