I managed to make a recognizable and quite edible Alfredo sauce. Although now that I've had almost a meal of it I think there's something missing...maybe needs more salt and/or pepper and/or Parmesan.
I started with melting some butter in a saucepan and then mixing in some flour. All I have is bread flour, so I used that. I went for my best guess as to what wallpaper paste consistency is. I then let the roux cook and tried to wait for it to get whiter. It bubbled a lot, and I didn't expect that. I don't know if that was boiling or if there was some sort of gas being released by cooking the roux. It got whiter, and at some point I couldn't tell that the parts around the bubbles or around the edge of the pan was whiter than the roux, so I poured some milk in.
Again I was surprised. The sauce immediately thickened into stiff dough, and I was afraid I was scalding the milk because the bottom of the pan got exposed and dry. I kept adding milk and stirring and realized that it wasn't burning after all. Still, I don't know if it was supposed to do that. Eventually it became a liquid sauce again, and I slowed then stopped adding milk. I had what I assume was béchamel. I then added some garlic powder, white pepper and grated Parmesan. I avoided salt for the moment because I planned to dump the cooked chicken breast in. The sauce thickened as I added cheese, so I added more milk. Then I cut up and put the chicken in. After a bit I turned the burner off and covered the pot to keep it hot. I hadn't prepared any pasta yet.
I boiled up some ancient bowtie pasta from the pantry, drained it, buttered and seasoned it then spooned my sauce and chicken into it. The chicken (from last post) was indeed overcooked and dry but edible. The sauce tasted great at first, but near the end of the meal I kept thinking it was missing something.
EDIT: Sean was horrified at this account and says Alfredo is not made with béchamel. We made it Saturday by boiling cream, adding parmesan and a little nutmeg and butter.