Heat oven to 350 degrees F. Grease bottoms only of 12 muffin cups or line with baking cups.
In a medium bowl, combine flour, sugars, baking powder, chocolate chips, and salt; mix well. In a small bowl, combine milk, oil, vanilla flavoring, sour cream and egg; blend well. Add dry ingredients all at once; stir just until dry ingredients are moistened.
Fill cups 2/3 full.
Bake for 20 to 25 minutes or until toothpick inserted in center comes out clean. Cool 1 minute before removing from pan. Serve warm.