1.Preheat oven to 425 degrees
2.Spray muffin pan with cooking spray with flour or butter flavored. Set aside. I used a silicone muffin pan and I still spray the inside of each cup.
3.In a large mixing bowl, using a hand held mixer, mix butter with sugar until combined. Add egg, mix, then add sour cream and vanilla if using. Mix again until smooth.
4.Add dry ingredients and mix by hand until all is incorporated. Make sure you get all the dry mixed into the wet. Try not to over mix.
5.Scoop into prepared muffin cups. Bake 15-17 minutes or until lightly browned on top and a toothpick comes out clean or with dry crumbs. The tops should also slightly spring back when touched lightly.
6.Let cool about 10-15 minutes. Pop muffins out and enjoy warm or at room temperature. YUM!