Preheat oven to 425 and line your muffin tin
In a bowl, whisk together the flour, sugar, baking powder, and baking soda
In a separate bowl, whisk together the sour cream, milk, eggs, and vanilla extract until smooth
Slowly whisk in the melted butter to the wet ingredients
Add the dry ingredients to the wet ingredients and gently fold until just combined
Fold in the blueberries
Divide the batter into the muffin tin, filling each cup generously (makes 12 regular muffins or 6 oversized muffins)
In another bowl, combine the flour, brown sugar, granulated sugar, cinnamon, and melted butter
Mix with a fork until a crumbly mixture forms
Generously sprinkle crumb topping over each muffin
Bake at 425 for 18-20 minutes for large muffins or 10-12 minutes for regular muffins
Allow to cool before serving
