Preheat oven to 400F. Grease twelve 1/3-cup muffin cups or line with paper muffin cups. Combine first 5 ingredients in large bowl. Whisk milk, butter, egg whites and vanilla to blend in medium bowl. Add milk mixture to dry ingredients, stirring until just combined. Mix in bananas and 1/2 cup pecans. Divide batter among prepared muffin cups. Sprinkle remaining pecans over each muffin. Bake until toothpick inserted into centers of muffins comes out clean, about 20 minutes. Transfer to rack to cool. Serve warm or at room temperature.