Heat oven to 400 degrees F. Place oven rack in center of oven. Lightly grease bottom and slightly up the sides of 12 muffin cups.
Combine flour, sugar, baking powder, cinnamon and salt in medium bowl. Stir several times until the cinnamon is well mixed in. Make a well in the center.
Beat milk, melted butter, vanilla and egg with a wire whisk in a medium bowl. Mixture doesn’t have to be completely smooth. Pour milk mixture into flour mixture and stir just until flour is moistened. Do not over mix. Batter can still be slightly lumpy. Divide batter into prepared muffin cups filling about 2/3 full.
Combine flour, sugar and cinnamon for streusel in a small bowl. Add cold butter and cut in with a pastry blender until mixture is crumbly. Sprinkle about 1 tablespoon streusel over each muffin.
Bake 18 to 20 minutes or until golden brown. Toothpick inserted in center of a muffin will come out dry.