Set the Instant Pot to Saute. Add 1 Tablespoon of the butter and stir until melted. Add the onions and cook, stirring until softened, 3-5 minutes.
Add the remaining butter and the flour and stir continuously until the flour disappears. Turn off the Instant Pot.
Add the garlic powder broth, half and half, dijon, salt pepper and nutmeg and stir to combine. Add the pasta and do your best to ensure all the noodles are covered. Add the spinach on top of the noodles, the spinach does not need to be covered by the liquid for the recipe to work out.
Set to manual high pressure for 5 minutes. When the cooking time is done, allow a natural pressure release of 4 minutes and then quick release any remaining pressure.
Stir through the parmesan, mozzarella and hot sauce. If the sauce is not as thick as you would like, turn off the keep warm button and replace the lid. Allow the dish to sit for 10 minutes or so for the sauce to thicken. Check for seasonings and serve.
