medium red or green bell pepper | 1 |
Cloves garlic | 3 |
medium yellow onion | 1 |
shredded sharp cheddar cheese (12 ounces), preferably white | 3 cups |
diced tomatoes or tomatoes with green chiles | 1 can |
dried spaghetti | 1 lb |
Breast meat from 1 rotisserie chicken, or about 4 cups shredded, cooked chicken (1 1/4 pounds) | |
unsalted butter | 4 tbsp |
kosher salt, plus more for the pasta water and seasoning | 2 1/2tsp |
all-purpose flour | 1/4 cup |
whole or 2% milk | 2 cups |
low-sodium chicken broth | 1 cup |
A rotisserie chicken and pantry ingredients makes this a weeknight-friendly version.
Boil a large pot of water and heat the oven to 375ºF. Bring a large pot of heavily salted water to a boil over high heat. Meanwhile, arrange a rack in the middle of the oven and heat the oven to 375ºF. Prepare the vegetables and cheese.
Prepare the vegetables, cheese, and tomatoes. Dice 1 bell pepper, mince 3 garlic cloves, and place both in a medium bowl. Dice 1 onion. Shred the cheddar cheese if needed until you have 3 cups. Drain the can of tomatoes into a fine-mesh strainer, rinse under cold water, and set aside to drain again.
Cook and drain the pasta. Break 1 pound spaghetti into 2-inch pieces and add to the boiling water. Cook according to package directions until al dente, 7 to 8 minutes. Drain and set aside. Meanwhile, prepare the chicken and start the sauce.
Shred the chicken. If using rotisserie chicken, shred the breast meat into bite-sized pieces, discarding the skin and bones; set aside.
Sauté the aromatics. Melt 4 tablespoons unsalted butter in a large Dutch oven or oven-safe pot over medium heat. Add the onion, season with 1/2 teaspoon of the kosher salt, and cook until softened, 5 to 6 minutes. Add the bell pepper and garlic and cook until the garlic is fragrant, about 1 minute.
Make the sauce. Add 1/4 cup flour and cook until the flour films the bottom of the pot, 1 to 2 minutes. Increase the heat to medium-high.
Add 2 cups whole or 2% milk, 1 cup low-sodium chicken broth, and the remaining 2 teaspoons kosher salt, and stir with a wooden spoon until smooth. Cook, stirring frequently and scraping the bottom of the pot, until simmering and thickened, about 4 minutes.
Add the cheese, tomatoes, chicken, and spaghetti. Stir in 2 cups of the cheese until melted. Remove from the heat. Stir in the drained tomatoes, chicken, and spaghetti until evenly combined. Taste and season with salt as needed.
Bake with more cheese on top. Sprinkle the remaining 1 cup cheese on top. Bake until bubbling, about 20 minutes. For a browned top, turn the oven on to broil and broil until the cheese is browned in spots, 4 to 6 minutes.
Cool 5 minutes before serving. Let the casserole cool 5 minutes before serving.