Completely line a 13x9 baking dish with foil and lightly grease. In a large bowl combine peanut butter, powdered sugar, honey and melted butter. Stir in 2 cups pretzel crumbs. Press mixture evenly into bottom of prepared dish to create a dense layer.
Heat butterscotch chips and evaporated milk in a medium sauce pan over low heat until melted and smooth, stirring occasionally. Pour and evenly over peanut butter layer. While still warm, sprinkle with 1/2 cup pretzel pieces and gently press in.
Cover and chill for at least 2 hours to set. Cut into bars with sharp knife. Store extras in air-tight container in fridge for up to 2 weeks.