Combine your peanut butter and butter in a medium-sized microwave-safe bowl and microwave in 10 second increments (stirring between each) until the butter is completely mixed into the peanut butter.
Stir in brown sugar and vanilla extract.
Gradually add the powdered sugar, about 1/4 cup at a time, stirring until completely combined. Set aside.
Roll about 1 Tbsp of your peanut butter mixture into a ball, slightly flatten to about 1/2" thickness, and set aside on a wax paper lined cookie sheet (if the peanut butter mixture is too sticky to handle, add more powdered sugar, stirring in 1 Tbsp at a time, until it is manageable).
Set out 20-22 cupcake liners**
Prepare your chocolate by placing the chocolate chips in a large, microwave-safe bowl and microwaving in 25-second increments (stirring well between each) until chocolate is completely melted.
Spoon a small amount (about 1 Tbsp) of chocolate into a cupcake liner until the entire bottom of the liner is covered.
Place a prepared peanut butter ball on top of the chocolate, and then spoon additional chocolate on top until all of the peanut butter is completely covered in chocolate.
Repeat until all cupcake liners have been filled.
Allow cupcake liners to sit undisturbed until the chocolate has hardened (this may take over an hour, depending on the temperature), or you may speed up the process and place the cups in the fridge for at least 30 minutes.