Bring the milk and salt to a simmer. When it is just barely simmering, whisk in the semolina flour. I usually end up pouring it in in three parts, because I can't whisk fast enough to get it all mixed unless I pause to do some extra whisking.
The mixture will thicken very rapidly. Switch to a wooden spoon and stir while cooking over low heat for about 5 min.
Stir in the butter, then the cheese, then the egg yolks. The batter will be quite stiff.
Pour in a baking dish (you can also use the kind of cookie sheet that has raised sides.)
Pat the mixture flat. I start with a spoon, then once a little heat drops, I switch to my hands. Let cool until stiff enough to cut into shapes (about 30 min.)
Let the mixture cool, then cut it into squares. Take the squares and put them at a slant in the baking dish, so they overlap but aren't one big mass. (Chef John's original recipe called for circles, but I don't have a circular cookie cutter, so squares it is.) Brush with butter and sprinkle on the remaining cheese.
Bake at 400*F for 20-25 min, until golden on top.
When these are fresh out of the oven, what is so tasty is the contrast between the crisp outer edges and the creamy center. But these keep well in the fridge and can be microwaved for a tasty snack. The contrast between crispy outside and creamy inside isn't as great, but they are still very tasty.