Preheat oven to 350°.
In medium mixing bowl, beat egg.
Mix in milk and oil.
Add in dry ingredients, stir until flour is incorporated but batter still lumpy. *Do NOT over mix.
Spray muffin tins with cooking spray.
Divide batter evenly into 12 muffins (or 24 mini muffins)
Bake 20 minutes for regular muffins, 18 for mini.
Using a butter knife, slip around each muffin and lift out of tin to cool on its side.
Melt butter in microwave or on stovetop.
Mix sugar and cinnamon in small bowl.
When muffins are cool enough to handle, roll in butter and then in cinnamon sugar mixture.