Bring 4 quarts lightly salted water to a rolling boil in a large pot. Cook the macaroni until al dente, about 8 minutes. Drain the macaroni in a colander, rinse with cold water to cool, and drain well. In a food processor, purée the cottage cheese until very smooth, scraping down the sides of the bowl with a rubber spatula. Preheat the oven to 400°F.

Have ready a large bowl of cold water. Place the flour in a 1-quart saucepan (preferably nonstick) over medium heat. Cook the flour, stirring with a whisk or wooden spoon, until it smells cooked, 3 to 5 minutes. (Quite suddenly, you'll notice a pronounced toasted smell.) Do not let the flour brown. Place the bottom of the saucepan in the bowl of cold water to stop the cooking. Set the pan aside until it and the flour are cool.

Add 1/4 cup of the milk and whisk to a smooth paste. Gradually whisk in the remaining milk. Bring the mixture to a simmer over medium-high heat, whisking steadily. Simmer for 3 minutes. Remove the pan from the heat. Whisk in the cottage cheese, mustard, Cheddar, Romano, and salt, pepper, nutmeg, and cayenne to taste: the sauce should be highly seasoned.

Stir the macaroni into the sauce. Spoon the mixture into an attractive 8 X 12-inch baking dish you've lightly sprayed with oil. Sprinkle the top with the bread crumbs. Bake the macaroni and cheese until bubbling, crusty, and golden brown, 20 to 30 minutes.