Put the macaroni, butter, salt and water in the pressure cooker. Lock lid and cook at high pressure for 4 minutes. Quick release pressure.
Place pressure cooker on saute and stir in evaporated milk.
Slowly add cheese about ½ cup at a time, stirring as it melts.
Keep it in low mode for about 5 minutes longer to thicken sauce.
If you like a crispy topping, remove from the pot and place in a baking dish. Top with breadcrumbs and grated parmesan. Bake at 400 for a few minutes until the top crisps up.
Recipe by Moola Saving Mom at https://moolasavingmom.com/pressure-cooker-mac-n-cheese-instapot/