In a large bowl, combine the flour, brown sugar, baking powder and salt.
In another bowl, combine the milk, butter, syrup, sour cream, egg and vanilla. Stir the wet ingredients into the dry ingredients just until moistened.
Fill greased or paper-lined muffin cups three-quarters full.
For the topping, combine the flour, sugar and cinnamon. Cut in the butter until crumbly. Sprinkle over batter.
Bake 16-20 minutes or until a toothpick inserted in centre comes out clean. (If desired, sprinkle with maple flakes or maple sugar when they are hot from the oven). Cool 5 minutes in the pan before removing from pans to wire racks. Serve warm. Yield: 10-16 muffins.