2) Gradually add the cheeses, reserving about 50g of each cheese for the top of the casserole. Stir the sauce thoroughly between each addition of the cheese. Simmer until the cheese is well blended.
3) Bring a large pan of salted water to a boil over high heat. Add the elbow macaroni and cook to al dente. Drain. Preheat the oven to 190C/Gas 5.
4) In a large casserole dish (or in several smaller dishes) add 1cm of the warm cheese sauce. Fill the casserole with the drained elbow macaroni. Top with another layer of cheese sauce, covering the macaroni completely and sprinkle with the reserved cheese.
5) Bake the macaroni until the top is brown, about 20 to 25 minutes. Cooking time will vary depending on the size of the casserole dish.
6) Remove from the oven and serve hot.
For the bechamel sauce:
1) In a small saucepan over low heat, melt 110g of the butter and add the onion. Saute until very soft, but do not brown.
2) In another saucepan, scald the milk. Stir the sauteed onions into the milk along with the salt, pepper and nutmeg.
3) Make a blonde roux by mixing the remaining 110g of butter and the flour in a small bowl. Add the roux to the simmering milk and cook until the mixture coats the back of a spoon.
Cook's note: The bechamel sauce can be prepared 1 to 2 days in advance and refrigerated.
This recipe was provided by professional chefs and has been scaled down from a bulk recipe provided by a restaurant. The Food Network chefs have not tested this recipe, in the proportions indicated, and therefore we cannot make any representation as to the results.