These blueberry muffins are bursting with juicy fresh blueberries and a sweet crumb topping. They're extra fluffy and moist — thanks to a secret ingredient in the batter!
Preheat the oven to 400°F. Line a muffin pan with 12 paper liners.
In a large bowl, whisk together the flour, baking powder, and salt. Set aside.
In a medium bowl, whisk together the melted butter, oil, sugar, milk, sour cream, eggs, and vanilla.
Fold the dry ingredients into the wet ingredients.
Gently fold in the blueberries. Fill the muffin liners 3/4 of the way full. Set aside.
In a bowl, mix together all the ingredients for the crumb topping with a fork until combined.
Sprinkle about one tablespoon of the crumb topping over each muffin.
Bake the muffins for about 20 minutes, or until they are baked through. Allow the muffins to cool for 5-10 minutes in the pan before transferring to a wire rack to continue cooling. Enjoy!