Preheat oven to 375 and line a muffin tin with liners or spray with grease.
In a medium bowl, add the flour, brown sugar, cinnamon, and salt.
Using a pastry blender or two knives, cut in the butter until incorporated fully and place into refrigerator until ready to use.
In a separate bowl, combine the flour, baking powder, and salt. Set aside.
In a medium bowl, cream the butter and sugar together.
Beat in the eggs, one at a time, and then slowly pour in the milk and vanilla extract.
Add dry ingredients to mixture slowly, stirring until just combined.
Scoop batter into prepared muffin cup, filling about 2/3 full.
Remove topping from refrigerator and sprinkle topping generously on top of muffin batter.
Place muffin tray into oven and bake for 20-23 minutes, or until toothpick comes out clean when inserted in center of muffin.
Remove from oven and allow to cool 2-3 minutes before serving!