Adapted from America's Test Kitchen
2 cups flour
1 tablespoon baking powder
1/4 teaspoon salt
1 cup sugar
1/2 stick (4 tablespoons) butter, melted and cooled slightly
1 1/4 cups sour cream
1 1/2 cups frozen blueberries (use wild if available)
Preheat oven to 350º. Line muffin tin with paper liners. Set aside.
Whisk flour, baking powder and salt in large bowl. Using another bowl or large Pryex measuring cup, whisk egg for about 20 seconds, add sugar and whisk well, then slowly add melted butter. Add sour cream and whisk to combine.
Add berries to dry ingredients and toss. Add sour cream mixture and fold in gently with spatula. Do not over-mix, but make sure no large pockets of flour remain.
Scoop batter into muffin tin. Bake till golden and toothpick inserted in center comes out clean, about 25-30 minutes. Remove muffins from pan to wire rack and cool slightly before serving.