With an electric mixer, beat the peanut butter and butter at medium speed until creamy. Reduce the mixer speed to low and mix in the confectioners’ sugar, vanilla, and salt (the mixture will be crumbly).
Roll tablespoonfuls of the dough into balls and place on a wax paper-lined baking sheet. Freeze until firm, about 15 minutes.
Meanwhile, in a double boiler or a medium heatproof bowl set over (not in) a saucepan of barely simmering water, melt the chocolate, stirring often, until smooth. Remove from heat and let cool slightly.
Resting each ball on the tines of a fork, lower it into the chocolate until it’s two-thirds covered. Refrigerate on the baking sheet until the chocolate is firm, about 30 minutes.
Storage suggestion: Keep the buckeyes refrigerated, between sheets of wax paper in an airtight container, for up to 3 weeks.