Step 1: In a large mixing bowl, combine the creamy peanut butter, softened unsalted butter, and vanilla extract. Beat with a stand mixer or hand mixer on medium speed until well combined and smooth, scraping down the sides of the bowl as needed.
Step 2: Gradually add the sifted powdered sugar, one cup at a time, mixing on low speed until combined, then increasing to medium until a firm, pliable dough forms. The mixture should be thick enough to roll easily into balls without sticking.
Step 3: Roll the peanut butter mixture into small, 1-inch diameter balls. Place the rolled balls onto a baking sheet lined with parchment paper or wax paper.
Step 4: Insert a toothpick into the top of each peanut butter ball, ensuring it's deep enough to hold it securely for dipping.
Step 5: Chill the peanut butter balls in the refrigerator for at least 30 minutes, or in the freezer for 15 minutes. This step is crucial for firming them up before dipping.
Step 6: Prepare the chocolate coating. In a microwave-safe bowl, combine the chocolate chips and shortening (if using). Microwave on 50% power in 30-second intervals, stirring well after each, until the chocolate is smooth and fully melted. Alternatively, melt over a double boiler.
Step 7: Remove the chilled peanut butter balls from the refrigerator. Holding a ball by the toothpick, dip it into the melted chocolate, leaving a small circle of peanut butter exposed at the top. Allow any excess chocolate to drip off.
Step 8: Gently place the dipped Buckeye back onto the parchment-lined baking sheet. Once the chocolate has slightly set, carefully remove the toothpick, smoothing over the small hole with your finger or a clean toothpick if desired. Repeat with all remaining Buckeyes.
Step 9: Allow the Buckeyes to set completely at room temperature for 1-2 hours, or chill in the refrigerator for 30 minutes until the chocolate is firm. Store in an airtight container in the refrigerator.