In a bowl, mix the peanut butter and softened butter until smooth. Slowly add the powdered sugar until the mixture holds together. Cover and chill in the refrigerator for 15 minutes.
Using clean hands, roll the chilled mixture into 1-inch balls. Place the balls on a parchment-lined baking sheet and refrigerate for about 20 minutes to firm up.
Melt the chocolate chips in a microwave-safe bowl in the microwave using 30-second intervals, stirring after each interval until smooth. If needed, add a splash of vegetable oil to the chocolate to thin it and make it more dippable.
Dip each chilled ball into the melted chocolate with a fork, letting excess chocolate drip off. Place the dipped balls on wax or parchment paper. If using, sprinkle on the sprinkles immediately. Chill until the chocolate is set.