Preheat oven to 375F and line a 12-cup muffin pan with paper liners. Set aside.
In a large bowl, whisk together the flour, brown sugar, baking powder, baking soda, salt and cinnamon.
In a large liquid measuring cup, whisk together milk, butter, eggs and vanilla. Add to dry ingredients and mix until batter is smooth. Fill muffin cavities 1/3 of the way full.
To make the cinnamon-sugar mixture, mix the sugar, brown sugar and cinnamon together in a small bowl. Add about 1 tsp. on top of the batter in each muffin cavity. Top with remaining batter until they are about 3/4 full.
To make the crumble topping combine dry ingredients with a fork. Add melted butter and mix until crumbly. Put a heaping tablespoon on top of the muffin batter.
Bake for about 17 – 20 minutes, until crumble is golden brown and a toothpick inserted into the middle comes out clean. Remove and let cool.