Place sliced potatoes into the Instant Pot with 1 cup of vegetable broth and cook on the manual pressure cooker setting for 1 minute. (standard pressure cookers, 1 minute on HIGH).Instant release the pressure once the timer expires.Preheat the oven on BROILTransfer the potatoes from the Instant Pot to a pie plate or other oven-safe dish leaving any cooking liquids in the Instant Pot. *There will not be a lot of liquid in there, but what does remain should be enough.Add the remaining ingredients (reserving 2 oz of cheese) to the Instant Pot and set to "Saute" and stir until smooth.Pour the cheese sauce over the potatoes in the dish and toss to evenly distribute the cheese sauce.Top with reserved cheese.Broil in the oven for 6 - 10 minutes until the top of the potatoes are bubbly and browned.Serve.