Preheat oven to 375°F with a rack in the center. Set aside a 9 x 13 x 2 inch baking dish.

Bring a big pot of well-salted water to a boil. Add the macaroni and cook until just al dente). Drain and set aside.

Meanwhile, make the cheese sauce. In a medium saucepan with a heavy bottom, melt the butter over medium heat.

Add the flour and whisk until well combined.

Cook for one minute, until frothy and just barely darkened in color.

Pour in the milk all at once. Add the bay leaf, nutmeg, cayenne, salt, and pepper and whisk well.

Raise the heat to high and bring to a boil, whisking frequently.

When the mixture boils, reduce the heat and simmer for five minutes, until slightly thickened. Remove from heat.

Remove the bay leaf. Stir in ¾ of the cheddar, all of the fontina or taleggio, and half of the parmesan. Keep stirring until cheese is completely melted.

Stir in the sour cream.

Pour drained macaroni into cheese sauce and stir to coat well, then tip the whole delicious mess into the baking dish and spread into an even layer.

Sprinkle with the remaining cheddar and parmesan.

Bake, covered with foil, for 30 minutes, then remove cover and bake 15 minutes more, until lightly browned and bubbly.