Pasta with onion sauce
Description
In a medium saucepan, melt the butter over medium heat. Add the onion and cook until soft, about 4 minutes. Stir in the flour and 1/2 teaspoon salt; cook, stirring frequently, until the mixture turns pale golden and has the consistency of oatmeal, about 5 minutes. Whisking constantly, gradually pour in 2 cups of milk. Add the remaining 2 cups of milk and the cayenne pepper, whisking until smooth. Bring to a boil, stirring continuously, in 6 to 7 minutes. Reduce the heat to low. Simmer, stirring, until the sauce thickens, about 10 minutes. Meanwhile, in a large pot of boiling salted water, cook the pasta until tender. Drain and return the pasta to the pot. Remove the sauce from the heat and let it cool for 10 minutes. Stir in the cheese, mustard, and Worcestershire sauce. Pour the sauce over the pasta and mix well.