Favorite dish of my children.
Melt the butter in a saucepan, gradually add flour and stir, lumps should come out.
Pour in milk (warm) a little at a time and stir until the lumps are dissolved. And cook until thickened.
Add salt, pepper.
Grate cheese on a fine grater.
Add cheese to sauce and stir.
Add the sauce to the finished hot pasta and mix, the cheese should stretch.
This item is not required, but still ... Transfer the pasta to a greased form, sprinkle with cheese and put in a preheated oven to 220 degrees for 10-15 minutes.