In a large bowl, combine the peanut butter, butter, powdered sugar, and milk, and use an electric hand mixer or whisk to beat until smooth.
Crush the pretzels in a large plastic bag using a rolling pin or heavy pan.
Transfer the crushed pretzels to a medium bowl, add the melted butter, and stir to combine.
Press the pretzel mixture into an ice cube tray. Top with a tablespoon of melted milk chocolate. Spread a small amount of peanut butter on top of the chocolate making sure it does not touch the side of the ice cube tray. Top with another teaspoon of milk chocolate. Freeze for at least 2 hours or up to 1 week.
Use a butter knife or offset spatula to loosen the chocolate from the ice cube tray. Flip the ice cube tray and let the pretzel bites fall out.
Let the chocolate pretzel bites thaw for 20 minutes before serving.