Ingredients:

  • 190g all-purpose flour
  • 200g granulated sugar
  • 1.5 tsp baking powder
  • 0.5 tsp salt
  • 115g softened butter, room temperature
  • 2 large eggs, room temperature
  • 120g full-fat sour cream
  • 1 tbsp vanilla extract
  • 65g dark brown sugar
  • 1.5 tbsp ground cinnamon
  • 1 tbsp all-purpose flour (for swirl)
  • 1 tbsp melted butter
  • 225g unsalted butter, softened
  • 480g powdered sugar
  • 1 tsp ground cinnamon (for buttercream)
  • 2.5 tbsp heavy cream
  • 1 pinch salt

Instructions:

  1. Preheat and Prep: Set your oven to 350°F (175°C). Line your 12 cup muffin tin with paper liners so they're ready to go.
  2. Make the Swirl Paste: In a small bowl, whisk together the 65g dark brown sugar, 1.5 tablespoons of cinnamon, 1 tablespoon of flour, and 1 tablespoon of melted butter. It should look like a thick, gritty paste.
  3. Mix Dry Ingredients: In your stand mixer, combine the 190g flour, 200g granulated sugar, 1.5 tsp baking powder, and 0.5 tsp salt. Run it on low for 30 seconds just to aerate everything.
  4. Add Butter: Drop the 115g of softened butter into the dry mix, one cube at a time, while the mixer is on low. Continue mixing until it looks like fine, sandy breadcrumbs.
  5. Incorporate Liquids: Add the 2 eggs, 120g sour cream, and 1 tbsp vanilla. Increase the speed to medium and beat for 60 seconds. The batter will turn pale and very smooth.
  6. Layer the Batter: Fill each cupcake liner about halfway. Drop a small teaspoon of the cinnamon paste right in the middle.
  7. Swirl and Top: Cover the paste with the remaining batter. Take a toothpick and swirl it through the layers in a figure eight motion. Stop before you over mix, or you'll just have a brown cupcake instead of a swirl.
  8. Bake: Slide them into the oven for 20 minutes. They are done when a toothpick comes out clean and the tops spring back when lightly touched.
  9. Cool Completely: Let them sit in the tin for 5 minutes, then move to a wire rack. If you frost them while warm, the buttercream will slide right off.
  10. Frost: Whip up your buttercream (225g butter, 480g powdered sugar, cinnamon, cream, and salt) until it's light and fluffy, then pipe it high. The magic happens in step 4. That sandy texture is exactly what you want. It might feel wrong if you're used to the traditional method, but trust the process. It's the secret to that tight, professional crumb.