Combine all the ingredients in the vegetable prep group together in the Instant Pot. Seal the lid, and cook on high (normal) pressure for 4 minutes then follow with a quick release. Drain the vegetables and put them back in the pot.
Add all the ingredients in the casserole topping group, and set the pressure cooker to saute. Stir until combined, and the cheese is melted.
Pour the mixture into a greased medium sized casserole dish. Layer the remaining cheese, and then the french fried onions on top.
Broil in the oven for ten minutes or until the cheese is melted and the onions are golden brown.