- Crumb Topping:
- 3 tablespoons sugar
- 1/2 cup dark brown sugar
- 1/2 teaspoon ground cinnamon
- 6 tablespoons unsalted butter, melted
- 1 1/3 cups cake flour
- Muffins:
- 2 cups cake flour
- 3/4 cup sugar
- 1 teaspoon baking powder
- 1 teaspoon baking soda
- 1/4 teaspoon salt
- 6 tablespoons unsalted butter, softened
- 1 cup sour cream
- 2 eggs
- 2 teaspoons vanilla extract
- Glaze:
- 1 cup powdered sugar
- 3 tablespoons Kahlua, or more as needed
- Preheat oven to 350 degrees F and line a muffin tin with liners.
- For the crumb topping combine the sugar, brown sugar, cinnamon, melted butter, and cake flour. Mix together until crumbly topping forms. Set aside.
- In the bowl of a countertop mixer with the paddle attachment, sift together cake flour, sugar, baking powder, baking soda, and salt. Stir until well combined. Add the softened butter and sour cream; mix until combined. Add eggs and vanilla. Mix just until liquid is absorbed. Batter may look lumpy.
- Fill the muffin cups about 1/2 full with batter. (Note: Do not add crumb topping yet.)
- Bake the muffins until the muffins are set but not quite fully baked, 23 to 25 minutes. Add a generous amount of crumb topping to the top of each muffin. Gently press the topping into the muffins. Continue baking until muffins are done, 8 to 10 more minutes. A toothpick inserted into the center of the muffin should come out almost clean once the muffins are done. Remove from oven and set on rack to cool slightly.
- While the muffins are cooling, make the Kahlua Glaze. Combine the powdered sugar and Kahlua in a small bowl. Stir together until a thick glaze forms.
- Drizzle the tops of the cooled muffins with the Kahlua Glaze.