Preheat oven to 375 degrees F. Spray your mini muffin pan with nonstick spray and set aside.
Mix sugar, butter, egg, vanilla and milk with a hand mixer in a large bowl. Add flour, baking powder and salt and continue to mix. Add in blueberries and stir gently with a spoon so you don't squash them.
Spoon mixture into your muffin pan evenly. This recipe makes approximately 16 mini muffins.
Now we're going to make the streusel. In a small bowl combine flour, brown sugar and cinnamon. Cut in your butter with a fork until it's crumbly. Add to the top of your muffins evenly.
Bake for 12-13 minutes or until the sides of your muffin are slightly golden brown. Remove from oven and allow to cool before serving.
