This is great on its own, but if you want to try something different, use one of the add-ins below.

SERVES 6 TO 8

INGREDIENTS

• Kosher salt
• 6 Tbs. unsalted butter
• 1 medium onion, finely diced
• 6 Tbs. unbleached all-purpose flour
• 1 Tbs. Dijon mustard
• 1 quart whole milk, heated
• 1 large sprig fresh thyme, plus 1 tsp. chopped thyme leaves
• 1 bay leaf
• 8 oz. (2 packed cups) grated extra-sharp white Cheddar (the sharpest you can find; I like Cabot® Seriously Sharp Hunter’s Cheddar)
• 4 oz. (1 packed cup) grated Monterey Jack
• 1/2 tsp. Worcestershire sauce
• 1/2 tsp. Tabasco sauce
• Freshly ground black pepper
• 1 lb. elbow macaroni or other small pasta, such as pipette or small shells
• 2 Tbs. extra-virgin olive oil; more for the baking dish
• 2 cups fresh breadcrumbs
• 1 1/2 oz. (1/2 lightly packed cup) freshly grated Parmigiano-Reggiano

INSTRUCTIONS

1. Preheat the oven to 400°F and bring a large pot of well-salted water to a boil over high heat.
2. In a 5-to 6-quart Dutch oven or other heavy-duty pot, melt the butter over medium heat. Add the onion and 1/2 tsp. salt and cook, stirring occasionally with a wooden spoon, until softened, 4 to 5 minutes. Add the flour and cook, stirring, until slightly darker, 1 to 2 minutes. Stir in the mustard. Switch to a whisk and gradually add the milk, whisking constantly.
3. When all the milk is in, switch back to the spoon and stir in the thyme sprig, bay leaf, and 1/2 tsp. salt. Let come to a bare simmer, and cook, stirring frequently, for 15 minutes to meld the flavors (reduce the heat to medium-low or low as needed to maintain the bare simmer).
4. Discard the thyme sprig and bay leaf. Add the Cheddar and Jack cheeses, stirring until melted, and then add the Worcestershire and Tabasco. Season to taste with salt and pepper. Keep warm, stirring occasionally.
5. Cook the pasta in the boiling water until al dente. Pour into a colander and shake it a few times to drain really well. Add the pasta to the cheese sauce and stir until well combined. Generously season to taste with salt and pepper. Lightly oil a 9×13-inch baking dish and spread the pasta in the dish.
6. In a medium bowl, toss the breadcrumbs, Parmigiano, olive oil, chopped thyme, 1/2 tsp. salt, and 1/4 tsp. pepper. Scatter the crumbs evenly over the pasta.
7. Bake until the crumb topping is golden, about 15 minutes. Let rest for 5 to 10 minutes before serving.

NUTRITION INFORMATION PER SERVING:

• 630CALORIES | 25g PROTEIN | 60gCARB | 32g TOTAL FAT | 18g SAT FAT | 10gMONO FAT | 2g POLY FAT | 80mgCHOL | 830g SODIUM | 3gFIBER

MAC AND CHEESE ADD-INNS:

• Pancetta or bacon: Sauté1/4lb. pancetta or bacon (finely chopped if using pancetta) until crisp and golden. Drain on paper towels, leaving the fat in the pan. Crumble the bacon, if using. Substitute the fat for part of the butter so that you have about 6 Tbs. total, and proceed with the recipe. Add the pancetta or bacon to the sauce along with the pasta.

• Ham :Brown 2 cups of small-diced smoked ham in the butter over medium-high heat. Drain on paper towels and proceed with the recipe, reducing the heat to medium to cook the onion. Add the ham to the sauce along with the pasta.

• Hot chiles: Cook 2 Tbs. minced fresh serrano chiles along with the onions. Or add1/4to1/2tsp. crushed red pepper flakes with the mustard.