In a large bowl, mix the peanut butter, softened butter, and vanilla extract until creamy. Gradually add powdered sugar, starting with 3 cups and adding more as needed, until a stiff dough forms. The mixture should be thick enough to hold its shape when rolled.
Scoop about a tablespoon of the peanut butter mixture and roll it into a ball. Place each ball onto a parchment-lined baking sheet. Repeat until all the peanut butter mixture is used.
Refrigerate the peanut butter balls for at least 1 hour to firm up. This step is essential for keeping the Buckeyes intact during dipping
In a microwave-safe bowl, melt the chocolate chips and shortening (if using) in 30-second intervals, stirring between each, until smooth.
Using a toothpick, dip each peanut butter ball into the melted chocolate, leaving a small circle of peanut butter exposed on top (this gives it the classic “Buckeye” look). Allow any excess chocolate to drip off, then place the Buckeye back onto the parchment-lined baking sheet.
Refrigerate the dipped Buckeyes for another 30 minutes or until the chocolate is fully set.
These Buckeyes are best served chilled and can be stored in an airtight container in the fridge for up to 2 weeks.