Preheat the oven to 375 degrees. Prepare muffin pans with muffin liners.
In a large bowl, add flour, sugar, brown sugar, baking powder, baking soda, cinnamon, and salt, and whisk together. Add milk and vegetable oil and stir. Add eggs, one at a time, incorporating each one before adding the other. Add vanilla and stir in.
Streusel: In a small bowl add butter, cinnamon, flour and brown sugar and mix together. Set aside.
Crumble: In a medium bowl add brown sugar, cinnamon, salt, softened butter, and flour and mix together with a fork until it comes together like crumbs. Set in the refrigerator while you make the muffin batter.
With an ice cream scoop add a little less than a full scoop to each muffin liner. **If making bakery size (large) muffins, add an overfull ice cream scoop to line.** Top the batter with the crumb topping.
Bake muffins for 15-17 minutes or until the center is done. Test with a toothpick to make sure it comes out of the center of the muffin clean.
While muffins are baking, make glaze. In a small bowl add powdered sugar, vanilla and milk and stir until smooth.
Remove muffins from the oven. Let them cool for at least 10 minutes. Top with glaze. Enjoy!