For the cake batter: Preheat the oven to 350 degrees F. Line a standard cupcake or muffin pan with 12 cupcake liners.
Combine the cake flour, baking powder, salt and baking soda in a small bowl and set aside. Combine the granulated sugar and butter in the bowl of stand mixer with a paddle attachment and mix on medium until creamy. While the mixer is running, add the eggs and yolks one at a time, thoroughly mixing after each egg; mix in the vanilla. Alternate adding the flour mixture and sour cream, ending with the flour. Stir in the pecans.
Fill the liners three-quarters full with the batter and bake until cooked through, about 20 minutes. Cool the cupcakes completely before frosting. Raise the oven temperature to 375 degrees F for the pie crust topper.
For the pie crust topper: In a medium bowl, combine the all-purpose flour, vegetable oil, pecans, milk, granulated sugar, brown sugar and salt. Mix with your hands and press onto a baking sheet into a rectangle about 1/4 inch thick. Bake until golden brown, about 10 minutes. Cool completely, and then brush on melted butter with a pastry brush. Use a round cookie cutter or another favorite shape to cut out pie crust toppers.
For the caramel drizzle: Combine the granulated sugar, butter and 1/4 cup water in a medium saucepan and cook on medium-high heat, whisking occasionally, until the sugar melts and becomes a dark amber color. Remove from the heat and slowly whisk in the cream. Add the salt and vanilla and continue to whisk until the caramel is smooth. Reserve 1/3 cup of the caramel for the buttercream, and set aside the remaining caramel for the drizzle.
For the caramel buttercream: Combine the brown sugar, salt and egg whites in the bowl of a heavy-duty stand mixer. Set the bowl over a medium saucepan of gently simmering water and whisk until the sugar is dissolved and the mixture is frothy and smooth and registers 160 degrees F on a candy thermometer, about 5 minutes.
Transfer the bowl to the stand mixer with a whisk attachment and beat on high speed until the mixture has cooled completely and formed stiff and glossy peaks, about 7 minutes. With the mixer running, add the butter one piece at a time. Continue beating until all the butter is incorporated and the frosting looks smooth. Stir in the reserved caramel drizzle and mix with a paddle attachment until fully incorporated and smooth.
To assemble, put a dollop of the caramel buttercream on each cupcake and place a pie crust topper on top. Drizzle with the reserved caramel drizzle.
This recipe was created by a contestant during a cooking competition. It has not been tested for home use.