Preheat the oven to 400 degrees. In a large bowl, combine flour, brown sugar, baking powder, and salt. In another bowl, combine milk, butter, syrup, sour cream, egg, and vanilla. Stir into dry ingredients just until moistened.
Fill greased or paper-lined muffin cups two-thirds full. For topping, combine flour, sugar, and cinnamon; cut in butter until crumbly. Sprinkle over batter.
Bake for 16-20 minutes or until a toothpick inserted in the center comes out clean. Cool 5 minutes before removing from pans to wire racks. Serve warm.
Serves: 16