I just made some alfredo sauce to go on past a for a late dinner - garlic, butter, milk, chives, parsley, fontina, romano, cheddar (cleaning out my cheese drawer), salt, pepper, cayenne, nutmeg, and a little flour, added in that order. I walked away from the stove for a minute, and when I came back it had separated into liquids & grainy solids. Why? I've never had hat happen before. It boiled over at one point, might that have to do with it? It was the same consistency as if I had poured lemon juice into a glass of milk. I poured some of it over pasta anyway, and ignoring the strange texture it was pretty delicious. Any idea how I can stop that from happening again?