In a large bowl using a handheld electric mixer or in the bowl of a stand mixer fitted with the whisk attachment, combine the peanut butter, unsalted butter, vanilla extract, and salt. Beat on low speed until combined.

With the mixer still on low, add the sifted confectioners’ sugar 1/2 cup at a time, beating well after each addition.

Add the milk and continue to beat until the mixture forms a workable dough. The dough will be slightly sticky but should be scoopable and easy to handle.

Add the finely chopped HEATH milk chocolate English toffee candy bars and mix on low speed until just combined.

Using a tablespoon measure, scoop 1 tablespoon-sized rounds of filling onto a large baking sheet lined with parchment paper. Roll each round into a smooth ball.

Press one honey roasted peanut on top of each ball, if using.

Place the baking sheet in the freezer and chill the balls until firm, about 1 hour.

During the last few minutes of chilling, melt the finely chopped 72% dark chocolate in a small heatproof glass bowl in the microwave on low power. Heat in 30-second increments, stirring after each increment, until completely melted. Stir in the espresso powder, if using, and whisk until smooth. Let the chocolate cool slightly before dipping so it is not too hot.

Remove the chilled peanut butter balls from the freezer. One at a time, carefully dip the bottom and sides of each ball into the melted chocolate so about 3/4 of the ball is covered and the top (with the peanut) remains exposed. Allow excess chocolate to drip back into the bowl, then transfer each dipped ball to a parchment-lined baking sheet.

Refrigerate the dipped buckeyes until the chocolate is set, about 1 hour. Serve chilled.