Using a stand mixer fitted with a paddle attachment or a large mixing bowl with a hand mixer, cream together the unsalted butter, vegetable oil, and sugar until the mixture is smooth and fluffy. Add the egg and vanilla extract, mixing well and making sure to scrape down the sides of the bowl to fully incorporate. In a separate medium-sized bowl, whisk together the cake flour, baking powder, baking soda, and salt until well combined. Gradually add the dry ingredients to the wet mixture and mix on low speed just until everything comes together. Add in the sour cream and mix gently until just incorporated, then pour in the warm milk and mix again until smooth. Scrape down the sides of the bowl one more time to ensure everything is well mixed—the batter should have a thick consistency.

In a small bowl, combine the brown sugar and ground cinnamon. Stir well and set aside; this will be used for the filling and topping.

Prepare a cupcake pan by lining it with paper liners. Spoon about 1 tablespoon of the cupcake batter into the bottom of each liner. Top with 2 teaspoons of the cinnamon-sugar mixture, then cover with another scoop of batter to enclose the filling. Finish by sprinkling a bit more of the cinnamon-sugar blend over the tops of each cupcake.

Bake in a preheated 350°F (175°C) oven for about 16 minutes, or until the edges are lightly golden and the centers spring back when touched. You can also test doneness by inserting a toothpick—it should come out clean.

While the cupcakes are cooling, prepare the cream cheese frosting. In a large bowl, whip together the softened butter and cream cheese on medium speed for 2 to 3 minutes until light and fluffy. Scrape down the sides of the bowl, then add the vanilla extract and powdered sugar. Continue whipping on high speed for about 30 seconds, just until the frosting is smooth and fully blended.

To make the cinnamon swirl frosting, scoop out ½ cup of the cream cheese frosting into a small bowl and stir in 1½ teaspoons of ground cinnamon. Transfer the cinnamon frosting into a piping bag.

Lay a large sheet of plastic wrap (Saran wrap) on a clean surface. Spread the plain cream cheese frosting in a log shape in the center. Cut the tip off the cinnamon frosting piping bag and pipe a long strip of cinnamon frosting alongside the plain frosting. Roll the plastic wrap tightly to create a frosting "log," then shape it into a form that can fit inside a piping bag.

Place the rolled frosting into a large piping bag fitted with a wide round tip. Cut off the end of the plastic wrap as well as the tip of the piping bag.

Once the cupcakes have cooled completely, pipe the frosting generously over the tops in a swirl pattern, resembling the iconic look of a cinnamon roll.

These cupcakes are best enjoyed fresh on the same day, but you can store them in an airtight container in the refrigerator for up to 2 days.

Enjoy every bite!