Preheat your oven to 350°F (175°C) and line a muffin tin with cupcake liners.
In a mixing bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
In another bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet ingredients, alternating with the milk. Mix until just combined.
Divide the batter evenly among the cupcake liners, filling each about two-thirds full. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Allow to cool completely.
For the frosting, beat together the peanut butter and butter until smooth. Gradually add the powdered sugar, beating until fluffy. Stir in the vanilla extract and milk until smooth.
Pipe or spread the peanut butter frosting onto the cooled cupcakes.
For the chocolate hi-hat, melt the chocolate chips and vegetable oil together in the microwave in 30-second intervals, stirring until smooth.
Dip the frosted cupcakes into the melted chocolate, allowing the excess to drip off. Let the chocolate set before serving.