Preheat oven to 375°F. Line 16 muffin cups with paper liners.
In a large mixing bowl, whisk together the flour, sugar, baking powder, baking soda, and salt.
In a medium bowl, whisk together sour cream, eggs, and vanilla extract.
Add the sour cream mixture to the flour mixture. Use a rubber spatula to stir gently, just until the ingredients come together and you can’t see any dry pockets of flour. Gently stir in the melted butter and oil. Do not over-mix. The batter will be very thick!
Fold in the blueberries.
Fill the muffin cups to the top with batter (I use an ice cream scoop to make sure that each muffin is the same size).
Sprinkle 1 teaspoon of coarse sugar on top of each muffin. It will seem like a lot of sugar for each muffin, but trust me – this is how you get those delicious bakery-style sugar-crusted tops!
Bake the muffins in the preheated oven for about 20 minutes, until a toothpick inserted in the center of a muffin comes out clean.
Let the muffins cool in the pans on wire racks for 5-10 minutes. Remove the muffins from the pans and enjoy warm, or cool completely before storing in an airtight container.