Step 1

Beat the peanut butter and butter in the bowl of a stand mixer fitted with a paddle attachment on medium until smooth and creamy, about 2 minutes. With the mixer on low, gradually add the powdered sugar, vanilla extract, and salt. Beat until smooth, 1 to 2 minutes, scraping the sides and bottom of the bowl, as needed.

Step 2

Using a tablespoon, divide the peanut butter mixture into about 28 balls; quickly roll in your palms until smooth (chill the buckeyes if they are getting too soft to work with). Place balls on a parchment paper-lined baking sheet and freeze for 30 minutes. Reshape balls once chilled, if needed.

Step 3

Fill the bottom of a medium saucepan with about 1 inch of water and bring to a simmer over medium-high heat. Place chopped chocolate in a dry, heat-proof glass or ceramic bowl that is slightly larger than the saucepan. The bowl should sit on top of the pan without its bottom touching the water.

Step 4

Reduce the heat to medium-low. Place the bowl of chocolate over the saucepan of water. Heat the chocolate, stirring occasionally with a dry rubber spatula, until chocolate is mostly smooth and melted, 3 to 5 minutes. Remove the bowl from the saucepan and continue stirring until the residual heat melts the remaining chocolate and mixture is smooth (return bowl to saucepan, if needed). Pour chocolate into a heat-safe mug.

Step 5

Skewer 1 peanut butter ball with a toothpick. Dip the ball 3/4 of the way in the chocolate, leaving a small round of peanut butter showing. Allow excess chocolate to drip off. Return the ball to the parchment paper-lined baking sheet. Sprinkle sides with jimmies, if desired. Remove the toothpick and carefully smooth over the hole.

Step 6

Repeat the dipping process with the remaining peanut butter balls. Reserve remaining melted chocolate for another use. Chill the buckeyes until the chocolate is set, about 30 minutes.