Preheat oven to 350 degrees.
Line muffin pan with liners.
Mix butter, sugar, eggs, vanilla and cinnamon until combined.
Add eggs, one at a time and beat until incorporated.
Add flour, baking powder, and salt and beat.
Pour in milk, a little at a time and beat until smooth and creamy.
Stir in chocolate chips.
Spoon batter into prepared muffin liners, filling about 3/4 full.
Sprinkle tops with granulated sugar or coarse sugar.
Bake muffins for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
Remove from oven and let sit in pan for 5 minutes, then move to a wire rack and cool.
Serve them warm, right out of the oven or at room temperature with or without butter.
Enjoy!