1. Preheat oven to 350F.
2. Mix together the melted butter, sugar, egg, vanilla, and milk.
3. Then add in all the dry ingredients (flour, baking powder, cinnamon, salt).
4. Mix halfway and add in the blueberries.
5. Fold in the blueberries until smooth.
6. Place the batter into muffin liners.
7. For the crumble topping, combine flour, white sugar, brown sugar, and melted butter. Sprinkle this topping on top of the muffins.
8. Bake for 22-25 minutes.
9. Let it cool down and enjoy!
