These Cinnamon Streusel Muffins are made from soft, moist and fluffy vanilla muffins filled with a rich cinnamon swirl filling, topped with a cinnamon and brown sugar crumble.
In a large bowl, whisk together the flour, brown sugar and ground cinnamon for the streusel topping. Work in the cold butter cubes until a sand like texture develops. Place the bowl in the fridge until the muffins are ready for topping.
In a small bowl whisk the brown sugar and ground cinnamon together until well combined. In a medium bowl whisk the all purpose flour, baking powder and salt together until well combined.
In a large mixing bowl, beat the butter and sugar together until light and fluffy. With the mixer on low, beat in the eggs, sour cream and vanilla extract one at a time until well combined.
Using a flexible spatula or on the lowest mixing speed, stir in the dry ingredients and milk into the wet,alternating in this order: dry, milk, dry, milk, dry.
Allow the muffin batter to rest for 20 - 30 minutes at room temperature. During this time, preheat the oven to 400 F (204 C). Line a 12 ct. muffin pan with cupcake or muffin liners.
Scoop a heaping tablespoon of muffin batter into each of the lined muffin wells. Top with a heaping teaspoon of cinnamon filling. Followed by another tablespoon of muffin batter on top of the filling. Top each of the muffins with a heaping tablespoon of the cinnamon crumble. Gently press the crumble into the muffins.
Bake the muffins for 10 minutes at 400 F (204 C). Reduce the oven temperature to 350 for the remaining time, about an additional 5-10 minutes.Cool the muffins in the hot muffin pan for 10 minutes. Enjoy!