Using a stand or electric mixer, combine the butter and peanut butter until smooth.
Add in the powdered sugar (1 cup to start) and mix until it has the consistency of a thick cookie dough. Add in the extra half cup little by little until you have the right consistency.
Melt your chocolate chips using the microwave (30 second intervals, stirring in between each one until smooth) or with a double boiler.
line a 24 mini muffin pan with the muffin liners.
Spoon a small amount of chocolate into the bottom of each liner. Tap the bottom of the pan onto the counter until the chocolate has spread to the bottom of the muffin liner.
Roll a small portion of the peanut butter into a ball and place in to each muffin liner.
Either spoon or squeeze the melted chocolate over top of the peanut butter balls, again tapping the pan to remove air bubbles and flatten the tops of the chocolate.