Preheat the oven to 350°F.
Add the white and brown sugar, and butter to a stand mixer. Beat on medium-high until well combined and creamy.
Add the egg, beating until well combined and resembles frosting, about 5 minutes (beat this longer than you think you need to, it helps add structure to the bars).
Stir in the beer and vanilla. The mixture may look a little curdled, this is fine.
Stir in the flour, baking powder, caramel or butterscotch chips and salt until just combined.
Line an 8x8 baking pan with parchment so that it comes up and over the sides (this makes for easy removal).
Spread the batter into the prepared pan in an even layer (it will be about the consistency of peanut butter). Bake for 40-45 minutes or until the edges just start to turn golden brown.
While the bars are still hot, sprinkle with chocolate chips then put back into the oven for 1 to 2 minutes or until the chips have just melted. Use the back of a spoon to gently spread the chocolate in an even layer.
Immediately sprinkle with pretzels and potato chips. Allow to cool until set and the chocolate has hardened.