In the bowl of a mixer, beat peanut butter and butter. Stir in vanilla. Add powdered sugar and beat on low speed until smooth.
Roll into small balls (about 1½-2 teaspoons worth) and sandwich between two pretzels. Place in the freezer for at least 1 hour.
Place the chocolate in a deep bowl and microwave for 10-15 seconds at a time, stirring between intervals, until melted.
Dip the chilled peanut butter pretzel balls into the melted chocolate and place on parchment or wax paper to set.
Video
Notes
I like these best when about half coated in melted chocolate. When I don't want them to be quite so sweet, I just drizzle a bit of chocolate on top, or alternatively, pour chocolate over the top. However, you coat them, they're delicious.