From my research the key is to grate your own cheese from a block and not to use pre-grated packaged cheese.
8oz pasta (I used large macaroni)
2 cups water or chicken
broth (I used water and a bit of bouillon)
1 teaspoon salt
2 Tablespoons butter
3 strips of cooked bacon broken into pieces
black pepper, to taste
Place in pressure cooker. Give a stir. Cook for 6 minutes on rice setting. Quick release and add...
1 generous cup of grated cheese (I used black pepper smoked white cheddar with a bit of medium cheddar)
Stir well to melt cheese.
Add some heavy cream to make it a bit smoother. Mine only needed a splash. But add what you like.