First, put on a pot of water for your pasta of choice. Fettuccine or linguine are common, but if all you have is spaghetti, that's fine too. We're not fancy.

When it's boiling, cook the pasta. If it finishes up a little early, drain and set aside, but it should finish up around the time everything else is ready.

A Note on Stirring: Sometimes people will tell you that you need to 'stir constantly' on a recipe like this. Yes, you do, but it's not going to get ruined if you need to remove the heat, set it aside for a moment, and do something else. 90-120 seconds of sitting there isn't gonna make much of a difference in your sauce.

Keep stirring, it should be getting pretty close to hot by now. Mix in the parmasean cheese and you guessed it, keep stirring. If all of the cheese is mixed in and melted, and it's still a little runny, you can make a very small corn starch + water slurry and mix that in, but be very careful you don't start the "add starch, now add milk, now add starch, now add milk" loop.

By now your chicken should be grilled, your pasta cooked and drained, and your sauce ready to go. I like to pre-slice the chicken before plating, then serve it on the top. Garnish with pepper if that's your thing.