Adapted and tested at high altitude from “Baking Illustrated”; makes 12-16 muffins, depending on pan size.
Ingredients
2 cups unbleached all-purpose flour
2 1/2 teaspoons baking powder
1/2 teaspoon table salt
1 large egg
1 cup (scant) granulated sugar
4 tablespoons ( 1/2 stick) butter, melted and cooled slightly
1 1/2 cups (10 ounces) sour cream
1 1/2 cups (8 ounces) fresh or frozen blueberries
TOPPING4 tablespoons butter, melted
1/3 cup sugar mixed with 1 teaspoon cinnamon
Directions
Adjust oven rack to middle position and heat oven to 350 degrees (325 convection). Spray standard muffin tin with nonstick vegetable cooking spray.
Whisk flour, baking powder, and salt in medium bowl until combined. Whisk egg in second medium bowl until white and yolk are well-combined and mixture is light-colored, about 20 seconds. Add sugar and whisk vigorously until thick and homogenous, about 30 seconds; add melted butter in 2 or 3 steps, whisking to combine after each addition. Add sour cream in 2 steps, whisking just to combine.
Add berries to dry ingredients and gently toss to combine. Add sour cream mixture and fold with rubber spatula until batter comes together and berries are evenly distributed, 25 to 30 seconds (small spots of flour may remain and batter will be thick). Do not overmix.
Use ice cream scoop or large spoon to drop batter into greased muffin tin. Bake until light golden brown and toothpick or skewer inserted into center of muffin comes out clean, 25 to 30 minutes, rotating pan from front to back halfway through baking time.
Remove muffins from oven onto wire rack, stand upright, and cool 5 minutes. After muffins have cooled enough to handle, dip in melted butter and cinnamon-sugar. Set muffins upright on wire rack; serve.
