Preparation Preheat oven to 375°F. Line muffin pan with liners. Whisk flour, granulated sugar, baking powder, and salt in a large bowl. Whisk eggs, sour cream, milk, and vanilla in a medium bowl. Mix egg mixture into dry ingredients, then stir in butter. Fold in blueberries. Divide batter among muffin cups, filling to the brim (about 1/2 cup batter per muffin). Sprinkle with coarse sugar. Bake muffins, rotating pan halfway through, until golden brown and a tester inserted into the center comes out clean, 28–33 minutes. Let cool in pan 5 minutes, then transfer muffins to a wire rack and let cool completely. Do Ahead Muffins can be made 3 days ahead. Transfer to an airtight container and store at room temperature, or freeze up to 2 months.