Preparation

• Preheat oven to 425°F (218°C). Spray a 12-count muffin pan with nonstick spray or use muffin liners. Set aside.
• For the topping: Mix all of the topping ingredients together. Set aside.
• For the muffins: Whisk the flour, baking soda, baking powder, and salt together in a large bowl. Set aside.
• Using a handheld or stand mixer, beat butter, granulated sugar, and brown sugar until smooth and creamy, about 3 minutes. Add eggs one at a time, beating well after each. Then add sour cream and vanilla, mixing to combine. Add dry ingredients and milk, mixing on low until combined. Fold in blueberries.
• Spoon the batter into liners, filling them all the way to the top. Spoon brown sugar topping on each, gently pressing it down into the surface so it sticks. Bake for 5 minutes at 425°F then reduce to 350°F (177°C) for an additional 18-20 minutes until a toothpick comes out clean.
• Allow muffins to cool for 5 minutes in the muffin pan, then transfer to a wire rack to continue cooling.
• Muffins stay fresh covered at room temperature for a few days or in the refrigerator for up to 1 week.