• Preheat the oven to 425°
• Line a muffin tin with liners or grease the tin well.
• In a large bowl, beat together the softened butter, granulated sugar, and the brown sugar.
• Add in the vanilla extract and eggs, mix.
• Beat in the sour cream until it is well blended.
• Add in the salt, baking powder, and baking soda.
• Blend the flour, careful not to overbeat.
• Add in the milk until mixed.
• Add 1 teaspoon of batter to 12 liners. Set aside.

Cinnamon Filling

• Mix together the melted butter, brown sugar, cinnamon, cocoa, salt, and flour.
• Combine until the mixture is crumbly
• Add a teaspoon of the mixture on top of the batter inside the muffin tins.

Making the Muffins

• After sprinkling 1 teaspoon of the mixture to the tins, fill the liners with the remaining batter all the way to the top. Gently press into the muffin batter.
• Sprinkle the rest of the crumb mixture
• Bake in the preheated oven at 425° for 5 minutes.
• Reduce the temperature to 350° and bake for 12-13 minutes.
• Remove from the oven and let cool on a wire rack.

Sweet Vanilla Glaze

• Combine 2 tablespoon of milk, ½ teaspoon of vanilla, and ½ cup of confectioner's sugar.
• Drizzle the glaze on the crumb topping once the muffins are completely cool.
• Store in an airtight container.