3 ounces freshly grated Pecorino Romano cheese (3/4 cup)
2 ounces freshly grated Parmesan cheese (1/2 cup)
2 tablespoons very finely minced parsley
Salt and freshly ground pepper
Preheat the oven to 350°. Position a rack in the upper third. Lightly butter a shallow 2-quart baking dish.
In a large pot of boiling salted water, cook the pasta until al dente. Drain, reserving 1/4 cup of the cooking water.
Meanwhile, in a small skillet, melt the butter over moderate heat. Add the garlic and cook until fragrant, about 1 minute. Add the oregano and cook for 30 seconds. Remove from the heat.
Return the pasta to the pot and add the Fontina, mozzarella, Pecorino and half of the Parmesan. Stir in the garlic butter, parsley and the reserved pasta water and season with salt and pepper.
Spread the pasta in the baking dish and sprinkle the remaining Parmesan on top. Bake for about 10 minutes, or until the cheese is melted. Turn on the broiler and broil the pasta for 1 minute, or until the top is golden brown. Serve.