In the bowl of a stand mixer fitted with the paddle attachment, combine the creamy peanut butter, softened butter, and vanilla extract. 

With the mixer on low speed, slowly add the powdered sugar. Continue mixing on low speed until the mixture comes together in a ball around the paddle. 

Scoop out 1 tablespoon-sized portions and roll them into smooth balls. Place the peanut butter balls on a parchment-lined baking sheet and transfer them to the freezer to chill for 30 minutes.

Add the dark chocolate and coconut oil to a microwave-safe bowl. Microwave in 30-second intervals, stirring well after each interval, until the chocolate is melted and smooth– about 1-2 minutes total. 

Working one at a time, stick a toothpick into the top of a peanut butter ball and then dip it into the melted chocolate, leaving a little bit of peanut butter exposed at the top. Then place the buckeye back on the baking sheet and repeat with the remaining buckeyes.