Preheat oven to 400°F. Lightly grease 12 muffin cups or line with paper baking cups. Set aside. For the Muffins, mix flour, baking powder, baking soda and salt in large bowl. Mix sour cream, brown sugar, milk, butter, egg and maple flavor in medium bowl until well blended. Add to flour mixture; stir just until dry ingredients are moistened.
Spoon batter into prepared muffin cups, filling each cup 2/3 full. For the Streusel Topping, mix all ingredients until crumbly. Sprinkle over muffins.
Bake 20 to 22 minutes or until toothpick inserted in center of muffins comes out clean. Serve warm.