In a large bowl, beat the peanut butter and softened butter together until smooth and creamy. Add the powdered erythritol, almond flour, vanilla extract, and salt. Mix until a thick, slightly crumbly dough forms.
Scoop tablespoon-sized portions of the dough and roll them into smooth balls between your palms. You should get about 24 buckeyes. Place them on a parchment-lined baking sheet.
Insert a toothpick into the top of each ball and freeze the baking sheet for at least 30 minutes until the balls are very firm. This step is essential for clean dipping.
Melt the chopped sugar-free dark chocolate and coconut oil together in a heatproof bowl set over simmering water, stirring until completely smooth and glossy.
Holding each ball by the toothpick, dip it into the melted chocolate about three-quarters of the way, leaving a circle of peanut butter visible at the top. Let the excess chocolate drip off, then return the buckeye to the parchment-lined sheet.
Remove the toothpicks and use a clean fingertip or the back of a small spoon to smooth over the holes. Refrigerate for at least 20 minutes until the chocolate is completely set and has a beautiful snap when you bite in.
Store in an airtight container in the refrigerator. Let them sit at room temperature for 5 minutes before serving for the best peanut butter texture.
