Place the macaroni in the instant pot and cover with water. Close and seal pressure valve and pressure cook on high for 5 minutes. Release pressure manually.
Drain pasta and set aside.
In a cast iron skillet over medium heat, melt the butter and whisk in the flour.
Once the flow and butter make a roux, Stein in the milk slowly to thicken the
mixture. Lowe the heat and add 2 cups of cheese.
Fold in the pasta and once coated, spread over the skillet.
Top with the remaining cheese and place under a high broiler until cheese
starts to brown.