Make the Streusel

1. Preheat oven to 400 degrees. Prepare a muffin pan with liners.
2. Add the sugar, flour and cinnamon to a medium-sized bowl. Cut the butter into the flour mixture until the butter is fully incorporated and the mixture is crumbly. Set aside.

Make the Muffins

1. Combine the flour, baking powder, baking soda and salt in a medium-sized bowl and set aside.
2. Add the melted butter, oil and sugars to a large mixing bowl and whisk together to combine.
3. Add the egg, vanilla extract and sour cream and whisk together until well combined.
4. Add the dry ingredients and gently stir until just well combined. Do not overmix. The batter will be thick.
5. Fold in the blueberries.
6. Fill the muffin cups about 3/4 full and divide the crumb topping between the muffins. You should get 12 muffins.
7. Bake the muffins for about 15-20 minutes, or until a toothpick comes out clean. Allow to cool for 3-5 minutes, then transfer to a cooling rack. Enjoy them while they’re still a little warm or let them cool completely.