In a medium bowl, use a mixer to combine the peanut butter and 1/4 cup butter.

Add the powdered sugar and vanilla, and continue mixing until combined and smooth.

Use your hands to shape 1 tablespoon of the peanut butter mixture into a patty. Repeat with the remaining peanut butter mixture.

Place the patties on a cookie sheet lined with waxed paper and refrigerate for about 30 minutes.

Melt the chocolate in a double boiler, or in the microwave in 30-second increments.

Add 2 tablespoons butter to the chocolate, and stir until the butter has melted and the mixture is smooth.

Spoon about 2 teaspoons of chocolate into the bottom of a cupcake liner.

Place a chilled peanut butter patty on top of the chocolate.

Spoon just enough chocolate on top to cover the patty. Repeat with the remaining chocolate and peanut butter patties.

Allow the peanut butter cups to set for a couple of hours before removing the cupcake liner.