Preheat oven to 400 F. and grease up twelve muffin cups. In a large bowl, stir together flour, sugars, baking powder, and salt. In another bowl, stir together milk, eggs, butter, and vanilla until blended. Make a well in center of dry ingredients; add milk mixture and stir just to combine. Stir in chocolate chips and nuts. Spoon batter into muffin cups; bake 15-20 minutes, or until a knife inserted in center of one muffin comes out clean. Remove muffin tin to wire rack; cool 5 minutes and remove from tins to finish cooling. Serve warm.