The Best Blueberry Muffins

1/2 c (1 stick) butter, room temperature
1 c sugar
2 eggs
1 tsp vanilla
2 tsp baking powder
1/4 tsp salt
2 1/2 c blueberries (mash 1/2 c with a fork)
2 c flour
1/2 c milk
1 tbsp sugar mixed with 1/2 tsp nutmeg

Heat oven to 375 degrees F. Grease 12 regular muffin cups or use foil baking cups. Beat butter until creamy. Beat in the sugar until pale and fluffy. Beat in eggs, one at a time. Beat in vanilla, baking powder, and salt. Mix mashed berries into batter. Fold in half the flour with a spatula, then half the milk. Add remaining flour and milk. Fold in remaining blueberries. Scoop batter into muffin cups. Sprinkle with nutmeg sugar. Bake 25-30 minutes or until golden brown. Let muffins cool at least 30 minutes in the pan before removing.