Place first portion of milk in a 2L capacity microwave bowl and heat on high power until boiling (approx 14 minutes, but watch very carefully toward the end, or it will boil over VERY quickly!).
Bring water & salt to boil in a large saucepan. Add macaroni once boiling, and cook til al dente (firm to the bite). Drain.
Add 2nd portion of milk, flour, chicken stock and seasoning to a shaker & shake til mixed. Add to boiled milk in jug and microwave again on high until boiling again.
Add most of the grated cheese to the milk mixture (which should now be thickened) and pour over pasta in oven proof serving dish.
Sprinkle leftover grated cheese on top and microwave until melted.
Serve with a salad, or you can add frozen peas/carrots/etc to the pasta while cooking if wanted. You can also add cooked bacon or ham to the recipe (add to pasta once drained, just before mixing with cheese sauce).