While the water is getting hot grate the cheese, taking out 2tbls of the Jarlsberg and the Gruyere. Also take 1 1/2 tbsp of the
Parmesan and set aside.
The cheese that you take away will be for sprinkling over the Mac and Cheese once you have it in the casserole.
In a microwave or two sauce pans heat the chicken stock and the milk separately until hot.
In the mean time grease the oven dish with butter and sprinkle in bread crumbs. Shake the dish to distribute the crumbs evenly, turn the dish upside down over the sink and tap out any extra. This will help to stop all that cheese from sticking to your baking dish.
Take a saucepan large enough to hold 1 1/2 liter or 1 1/2 quarts of liquid. Over medium heat melt
the butter and whisk in the flour and let this cook for about 3 minutes so the flour will take the liquid. Using a whisk add the chicken stock a little at a time until it thickens, then do the same with the milk keeping back a little if the sauce is becoming too thin.
Add the salt, pepper, nutmeg and Dijon mustard. Then add the grated cheeses keeping the little extra that you took out.
Take the cooked pasta drain and return it to the pot, add the sauce and the cubed cooked meat, mixing well. Taste for salt and pepper.
Now pour the mixture into the oven dish, sprinkle over the reserved cheese and then the bread crumbs. Dot with a little butter and put into the middle of a 200°C or 400°F oven for about 40 minutes or until the dish is bubbling and nicely browned on top.
Remove and let sit at least 10 minutes before serving with a nice salad.