Ingredients

• 1 lb. 

  spaghetti

• 1 tbsp. 

  extra-virgin olive oil

• 1 

  yellow onion, chopped

• 1 

  red bell pepper, seeds and ribs removed, chopped

• 1 lb. 

  boneless, skinless chicken breasts, cut into 1" pieces

• Kosher salt

• Freshly ground black pepper

• 1/2 tsp. 

  chili powder

• 3 tbsp. 

  unsalted butter

• 3 tbsp. 

  all-purpose flour

• 2 c. 

  whole milk

• 1 c. 

  low-sodium chicken broth

• 2 1/2 c. 

  shredded cheddar, divided

• Chopped fresh parsley, for serving

Description

1. Step 1Preheat oven to 350°. In a large pot of boiling salted water, cook spaghetti, stirring occasionally, until al dente according to package instructions, about 7 minutes.
2. Step 2Meanwhile, in another large pot over medium heat, heat oil. Add onion and bell pepper and cook, stirring occasionally, until softened, about 7 minutes. Transfer to a plate.
3. Step 3Season chicken all over with salt, pepper, and chili powder. In same pot over medium-high heat, cook chicken, stirring occasionally, until golden brown, about 5 minutes. Transfer to another plate.
4. Step 4In same pot over medium heat, melt butter. Whisk in flour and cook, whisking constantly, until fragrant and combined, about 1 minute. Add milk and broth and cook, stirring occasionally, until thickened, about 5 minutes.
5. Step 5Stir in spaghetti, vegetables, chicken, and 1 1/2 cups cheddar. Transfer to a 13" x 9" baking dish. Top with remaining 1 cup cheese.
6. Step 6Bake chicken spaghetti until bubbly, about 45 minutes. Top with parsley.