1. First preheat your oven to 350 degrees and line your muffin tins with paper liners. 
2. In large mixing bowl, add cake flour, baking powder, and baking soda. Whisk to blend. Set aside.
3. In stand mixing bowl and paddle attachment, add softened butter, brown sugar, oil and salt.  Whip on medium -high speed until light and fluffy about 5 minutes. Make sure your butter is at room temperature.
4. Scape down sides and bottom of bowl, add one egg white at a time then one yolk mixing well between each addition.
5. Decrease speed to low and add dry ingredients, alternating with buttermilk, beginning and ending with flour.  Stop mixing when just a few streaks of flour show through, then fold by hand the remaining streaks with large rubber spatula. This helps with texture of your cake batter, no tunnels after baking.
6. Using 2″ scoop fill cupcake liners 2/3 full. Run a knife through the cupcake batter to remove any air bubbles. Bake cupcakes in middle of oven at 350 for 20 minutes.  The cakes are done when toothpick tester inserted in the center comes out clean.  Allow cupcakes to cool about 5 minutes in pan before removing from tin.

Making Buttercream

In large mixing bowl of stand mixer fitted with whisk attachment, combine butter and confectioner’s sugar. Beat on low speed, then scrape down sides and bottom of mixing bowl.  On low speed add 4 tablespoons of dulce de leche, whip to combine, then add 4 additional tablespoons, beat in cream 1 tablespoon at a time until spreadable consistency. Beat on high speed until light and fluffy. Cover bowl with tea towel until ready to frost cupcakes.

Assembly

1. Fit large piping bag with tip 1 M. Fill bag with buttercream.  Pipe one large swirl on top of cupcakes.
2. Place caramel corn on top of frosting crown as desired and sprinkle with peanuts.
3. In small custard cup spoon 4 tablespoons of dulce de leche, add 1/2 teaspoon cream, microwave 12 seconds to melt slightly.  Stir until combined. Drizzle over tops of cupcakes. Sprinkle with coarse sea salt if desired.

To Decorate a 6″ Cake

Place cake on 6″ round cake board, Add a touch of frosting on the board to keep the cake from slipping.  Top with 1 cup frosting, spread evenly.  Add next cake layer. Then frost entire cake in thin coat (crumb coating) of frosting.

Smooth sides and top of cake with off set spatula until smooth.  A bench scraper or cake smooth will help smooth sides.

Place remaining frosting in piping bag, pipe swirls on top of cake-at 12, 3, 6 and 9 positions on top of cake.

Melt dulce de leche in microwave a few seconds to thin, drizzle sauce between swirls and on top of the cake allowing to drip slightly down the sides of cake.

Fill center of cake with caramel corn and peanuts, drizzle with more caramel sauce if desired.  Sprinkle with sea salt.