Preheat the oven to 350°F. Grease a 12-count muffin pan with the cooking spray. Set aside.

To make the topping: In a medium mixing bowl, combine ½ cup of the flour, the brown sugar, and ½ teaspoon of the cinnamon. Using your fingers, a pastry blender, or the tines of a fork, cut 4 tablespoons of the butter into the flour mixture until it becomes crumbly. Set aside.

To make the batter: In the bowl of a stand mixer fitted with the paddle attachment, sift together the remaining 2 cups of flour, the remaining 1 teaspoon of cinnamon, the baking powder, and the salt. Add the granulated sugar, the remaining butter, and the vanilla extract and mix for 2 to 3 minutes on low speed. Set aside.

In a small mixing bowl, combine the sour cream, eggs, and baking soda. Stir until well combined. With the mixer running at low speed, slowly add the sour cream mixture to the flour mixture ⅓ at a time and beat for 2 to 3 minutes, until well combined. Turn off the mixer.

Divide the batter evenly among the cups of the prepared pan, filling each about ⅔ full. Sprinkle each evenly with the topping. Bake for 20 to 25 minutes, until a wooden toothpick inserted into the center of a muffin comes out clean. Remove from the oven and set aside to cool in the pan on a wire rack for 10 minutes.

To make the glaze: In a small mixing bowl, whisk together the confectioners’ sugar, milk, and vanilla extract until fully combined. Drizzle the glaze over the muffins.

Using a serrated knife, separate the muffins from the pan and then tap the pan gently on the counter to release them.

Transfer to a serving platter and serve warm.