Line a baking sheet with wax paper and set aside.

In the bowl of a stand mixer fitted with the paddle attachment, beat peanut butter and butter until combined. Scrape down the bowl, add sugars and beat until combined. You should be able to roll the mixture into balls without it sticking to your hands. If needed, add more powdered sugar until you reach a consistency that is easy to roll.

Roll the mixture into small balls, about 1 teaspoon of mixture for each ball, and place on the prepared baking sheet. Sandwich the balls between two pretzels and place in the freezer for 30 minutes.

Melt the chocolate in a double boiler or a bowl over a pan of lightly simmering water. Stir occasionally until smooth, and remove from heat. Dip each pretzel bite halfway into the melted chocolate and place on the prepared baking sheet. Sprinkle lightly with fleur de sel before the chocolate hardens. Chill in refrigerator until chocolate is set.

(Recipe adapted from Foodaphilia.)