1In a large Dutch oven or wide, heavy-bottomed pot, heat the butter and olive oil over medium-low.
2Add the onions and cook, stirring every few minutes, until deeply browned, soft and jammy, about 45 minutes.
3Once the onions are caramelized, add ¾ teaspoon salt, several grinds of black pepper, the garlic, thyme and Worcestershire sauce and cook until fragrant, about 30 seconds.
4Pour in the white wine and cook, scraping up any browned bits from the bottom of the pot, until mostly reduced, about 30 seconds.
5Add the rigatoni to the pot, then pour in enough broth to just cover the pasta.
6Bring to a boil, then reduce the heat to medium and cook uncovered, stirring every 1 to 2 minutes, until the pasta is just tender and the liquid has thickened into a sauce, 15 to 18 minutes depending on the brand and thickness of the pasta.
7If the liquid reduces too quickly (before the pasta is tender), add more broth, if you didn’t use it all, a splash at a time.
8Lower the heat and stir in the heavy cream.
9Remove the pot from the heat.
10Add the Gruyère a small handful at a time, stirring until fully melted and smooth before adding more.
11Once the Gruyère is fully incorporated, stir in the Parmesan until the sauce is glossy and coats the pasta evenly.
12Taste and adjust seasoning with additional salt and pepper if needed.
13Let rest for 5 to 7 minutes before serving to allow the sauce to tighten.
14Serve warm, with extra Parmesan if desired.
Ingredients
2 tablespoons unsalted butter
1 tablespoon olive oil
2 large yellow onions, thinly sliced
Kosher salt (such as Diamond Crystal)
freshly ground black pepper
2 garlic cloves, minced
1 teaspoon fresh thyme leaves
2 teaspoons Worcestershire sauce
0.25 cup dry white wine
5 to 6 cups broth (beef recommended for deeper flavor, chicken for a lighter profile; vegetable broth also works)
1 pound mezzi rigatoni or regular rigatoni
0.5 cup heavy cream
1 cup shredded Gruyère cheese (about 5 ounces)
0.5 cup finely grated Parmesan cheese (about 2 ounces), plus more for serving (optional)
Equipment
large Dutch ovenwide, heavy-bottomed pot
Tips
Yellow onions are ideal as they caramelize evenly and develop deep sweetness without becoming cloying.
For a heavy cream substitute, use half-and-half or even whole milk.
For cheese, while Gruyère is classic, mozzarella is also a lovely option.
When cooking pasta, if the liquid reduces too quickly, add more broth a splash at a time.
Let the pasta rest for 5 to 7 minutes before serving to allow the sauce to tighten.
To speed up caramelization, add a quarter teaspoon of baking soda to the onions in Step 1.
Sprinkling onions with about 1 teaspoon sugar helps speed up and even out the caramelization process.
To add color, include a handful of escarole, chopped parsley, or chopped sweet red pepper.
If you want more protein, try adding a fried or soft-boiled egg.