Preheat the oven to 350 degrees F. Line a 9x13-inch baking dish with parchment paper. In a medium bowl, mix the flour, baking powder and salt together.
Using an electric mixer, beat the butter and sugar together until light and fluffy. Scrape the bowl and add the eggs and vanilla. Beat to combine. Then slowly add the flour mixture until just combined. Scrape the bowl again, and stir in the crumbled potato chips.
Dump the dough into the baking dish and press flat with your hands. Bake for 30 minutes, until golden on top. Then cool completely before preparing the topping.
Pour the sweetened condensed milk, chocolate chips and butter in a microwave-safe bowl. Microwave in 30 second increments, stirring in between, until the mixture is completely smooth. (Should take no more than 2 minutes total.) Pour the fudge topping over the cookie bars and smooth with a spatula. Then sprinkle the top with the remaining crumbled potato chips.
Place in the fridge just long enough for the fudge topping to harden, then lift the whole sheet of bars out of the pan by the edges of the parchment paper and cut.