Make the Peanut Butter Mixture: In a large bowl, beat peanut butter, butter, and vanilla with a mixer until smooth and creamy.
Add Sugar: Gradually add powdered sugar, mixing until the dough is thick but not crumbly. The mixture should hold together when rolled.
Shape into Balls: Scoop 1-inch portions and roll into smooth balls. Place on a parchment-lined baking sheet. Chill in the refrigerator for 30 minutes.
Melt the Chocolate: In a microwave-safe bowl or double boiler, melt chocolate chips with shortening (if using), stirring until glossy and smooth.
Dip the Buckeyes: Insert a toothpick into each chilled peanut butter ball and dip ¾ of the way into chocolate, leaving a circle of peanut butter exposed. Let excess drip off.
Set and Store: Place dipped buckeyes back on parchment. Refrigerate until chocolate is set. Smooth over toothpick holes if desired. Store in an airtight container in the fridge.