• Preheat the oven to 350 degrees F. In a bowl, whisk together the flour, baking soda, salt and spices. Set aside. Line a muffin tin with liners.
• In a large bowl, whisk the egg and brown sugar together until smooth and no lumps remain. Add in vanilla extract, butter and bananas, whisking again until combined. Gradually add in dry ingredients, mixing until just incorporated. Stir in the milk and mix until just combined. Fill each muffin liner 2/3 of the way full with batter (I use a 1/4 cup measure to get the muffins to be of equal size). Top them with the crumb topping.
• Bake for 15-17 minutes, or until tops are no longer wet and become slightly golden. Remove and let cool until cool to the touch.

crumb topping

• To make the crumb topping, whisk together the sugar, cinnamon, salt and melted butter until combined. Whisk for a a good minute or two until the sugar begins to dissolve, then use a wooden spoon to stir in the flour. The mixture will be crumb-like and dry. Almost like a sludge or paste. This is what you want! Sprinkle the crumb on top of the cake.