Preheat oven to 400 degrees. Add flour, brown sugar, salt and baking powder to a large bowl.
1
In a medium bowl add sour cream, vanilla, vegetable oil and egg. Whisk to combine.
2
Add egg mixture to dry ingredients and fold gently until combined. Fold in blueberries. Do not over mix.
2
Scoop batter into a muffin pan lined with baking cups. Fill almost all the way up. Sprinkle each muffin generously with streusel.
3
Place in the oven and bake for 20 minutes or until muffins are set. Stick a toothpick or knife in the center and make sure it comes out clean.
3
Add butter, brown sugar, flour and cinnamon to a small bowl. Mix together until the streusel forms a crumb like texture similar to wet sand.
4