For the Cakes:

1. Preheat oven to 350°F. Line a standard muffin tray with paper liners; set aside.
2. In a small bowl, combine the flour, baking powder, and salt; set aside.
3. In the bowl of an electric mixer fitted with the paddle attachment, cream together the butters and sugars on medium speed for at least 5 minutes. Add in the eggs and vanilla extract, and beat for another couple of minutes.
4. Now, add in half of the flour mixture and mix on low to combine. Scrape down the sides and paddle and add in the milk and mix on low to combine. Follow with the remainder of the flour mixture and combine. Add in the peanut butter and mix on low, with a few bursts of high speed, until combined.
5. Fill the paper liners 3/4 of the way full (I find it’s easiest to fill them with a large cookie scoop), Bake for 17-20 minutes, or until a toothpick inserted into the center comes out clean.
6. When the cupcakes have cooled, use a cupcake corer, apple corer, or paring knife to remove a center plug of each cupcake. Fill the holes with around a teaspoon of jam each, and replace the cupcake plug. I like to warm the jam a bit in the microwave to make it a bit more pourable, and then put it into a squeeze bottle.

For the Frosting:

1. Place the butter in the bowl of an electric mixer fitted with the paddle attachment. Beat on high for about 30 seconds to loosen it up. Add in the sugar, 1/4 cup at a time, mixing on low after each addition until combined.
2. Scrape down the sides and add in the peanut butter and salt. Beat on high speed for 5-7 minutes until increased in volume and somewhat stiff.
3. Pipe or spread the frosting onto the cupcakes, top with a drizzle of jam, and some sprinkles.