I highly recommend making the salted caramel and the brown butter for the buttercream the night before so that they both have time to fully cool!
Cupcakes
Preheat the oven to 350°F and line a 12 cup cupcake pan with cupcake liners.
Whisk the cake flour, cornmeal, baking powder, and salt together in a large bowl.
In a separate bowl, whisk together the brown butter, brown sugar, and granulated sugar until smooth.
Then whisk in the eggs and vanilla until fully combined. Add in the sour cream and whisk until smooth.
Gently fold in the flour mixture until fully incorporated.
Pour about ¼ cup of batter into each cupcake liner (they should be about halfway full).
Bake at 350°F for 18-22 minutes or until a cake tester comes out clean.
Remove from pan and let brown butter cupcakes cool on wire rack.
Caramel Buttercream
In a large bowl using a handheld or stand mixer fitted with a paddle attachment, cream the butter until smooth.
Add in the powdered sugar ½ cup at a time until fully combined and smooth.
Set the mixer to low speed and slowly drizzle in the salted caramel until it's fully incorporated into the buttercream.
Then beat on high speed for 3-4 minutes or until the buttercream is super light and fluffy. If needed, add in cream 1 tablespoon at a time until desired consistency is reached.
Frost the cooled cupcakes, then garnish with homemade caramel popcorn and extra caramel drizzle!
Notes
These popcorn cupcakes are best eaten immediately! The caramel corn will start to soften and lose its crunch the longer it's in contact with the frosting. Store the frosted cupcakes in the fridge for up to 3 days, but wait to garnish with popcorn until right before serving.To make brown butter, melt unsalted butter over medium heat, stirring frequently. Watch closely for the butter to develop brown specs and a nutty aroma. Once you start seeing brown specs, let cook for just a few seconds longer (watch very carefully or it will burn). Remove from the heat and pour into a small bowl so that it doesn't continue to cook. Set aside and let cool for about 20 minutes in the fridge until soft and pliable. Note: For every ½ cup (1 stick or 113g), you'll lose about 1 tablespoon (14g) to evaporation while cooking. So you can either add in an extra 1 tablespoon before browning, or if you're browning big batches, just make up the weight difference in your recipe with regular unsalted butter if needed.