Vanilla Cupcakes

1. Preheat oven to 325F (165C). Fill a 12-count cupcake baking pan with 12 cupcake liners.
2. In a medium mixing bowl, add the flour, baking powder, baking soda and salt. Whisk ingredients together to combine. In a small mixing bowl/measuring cup, add the milk and vinegar and whisk to combine.
3. In the bowl of a stand mixer fitted with paddle attachment or with a hand-held electric mixer and large mixing bowl, cream the butter, oil and sugar together until mixture appears thick and fluffy in appearance, about 2-3 minutes.
4. Beat the eggs into creamed butter mixture one at a time allowing the initial egg to be fully incorporated before mixing in the next egg. Next, mix in the vanilla extract into wet batter.
5. Reduce mixer speed to low. In an alternating fashion, starting and ending with the flour mixture, mix half of the flour mixture into wet batter, followed by all of the milk-vinegar mixture and ending with the remaining flour mixture.
6. Stop mixer and use a rubber spatula to scrape the sides and base of mixing bowl. At medium speed, mix cupcake batter for an additional 30-60 seconds to ensure you have a smooth batter.
7. Evenly scoop cupcake batter into prepared cupcake pan and bake for 18-20 minutes, rotating the pan halfway through bake time. Cupcakes are ready when a toothpick inserted into one of them comes out clean.
8. Cool cupcakes in baking pan for 4-5 minutes before transferring to a cooling rack to cool completely to room temperature. 

Peanut Butter Caramel Sauce

1. In a small, heat-safe mixing bowl, add the caramel sauce and peanut butter. Whisk to combine. Heat up peanut butter caramel mixture in the microwave on high for 10-15 seconds to loosen up sauce into a pourable but not too runny consistency.
2. Transfer 3/4 of peanut butter caramel sauce into a large pastry bag. Set aside until ready to use. Reserve the remaining 1/4 of sauce for drizzling over piped buttercream.

Peanut Butter Caramel Buttercream

1. In a stand mixer fitted with paddle attachment or in a large mixing bowl with a hand-held electric mixer, cream the butter and salt together at medium high speed until mixture is smooth and fluffy in appearance, about 2-3 minutes.
2. Mix the peanut butter and caramel sauce into creamed butter at medium speed until fully incorporated, about 1 minute.
3. Reduce mixer speed to low and mix in 2 1/2 cups of the confectioners’ sugar into peanut butter caramel mixture. Gradually increase mixer speed back to medium.
4. Once all of the sugar has been incorporated into peanut butter caramel mixture, mix in the vanilla extract and 1 tablespoon heavy whipping cream into peanut butter caramel buttercream.
5. If buttercream appears to be on the soft side, mix in the remaining confectioners’ sugar 1/4 cup at a time until a thick but pipeable consistency is reached. If buttercream appears too thick, mix in remaining heavy whipping cream, 1 teaspoon at a time until the desired consistency (thick but pipeable) is reached.
6. Increase mixer speed to medium high and mix peanut butter caramel buttercream for an additional 30-60 seconds. The resulting buttercream should be smooth and fluffy in appearance.

Assembly 

1. Transfer peanut butter caramel buttercream into a large pastry bag fitted with a 6B or preferred pastry tip.
2. Core the center out of cooled cupcakes, about 1 inch. Take care to not core all the way to the bottom of cupcakes. I used this tool but this treat corer is a good alternative as well.
3. Cut a 1/4 inch off pastry bag filled with peanut butter caramel sauce and pipe filling into the centers of cored cupcakes.
4. Next, pipe peanut butter caramel buttercream on top of filled cupcakes in a swirl or preferred design.
5. Drizzle remaining peanut butter caramel sauce over piped buttercream and sprinkle with finely chopped peanuts. (If peanut butter caramel sauce thickened up and is no longer pourable, simply re-warm in the microwave on high for 5-10 seconds.)