Preheat oven to 425°F. Line 12 muffin cups with liners or lightly spray with nonstick spray.

In a medium bowl, whisk together topping ingredients: flour, brown sugar, cinnamon, and salt. Cut in the butter until completely incorporated. Mixture should be crumbly and hold together when squeezed between your fingers. Keep in refrigerator until ready to use.

In a medium mixing bowl, whisk together flour, baking powder, baking soda, salt, and cinnamon. Set aside.

In a large mixing bowl, cream butter and sugar. Beat in eggs one at a time. Use a wooden spoon to stir in milk and vanilla.

Add dry ingredients and using a wooden spoon stir just until combined. If you still see small streaks of flour that's okay.

Scoop batter into prepared muffin tin. Sprinkle generously with streusel topping, pressing down firmly on the tops to ensure that it sticks. Each cup should be full once the streusel is added.

Bake muffins at 425 F for 5 minutes. Then reduce the temperature to 350 F and bake another for 12-15 minutes, or until a toothpick inserted in the center comes out clean. Hitting the muffins with a few minutes of high heat helps create a large muffin dome.

Cool for 5 minutes in pan, then remove to wire rack to cool completely.