Preheat your oven to 350°F (175°C) to ensure it's ready for baking later. Meanwhile, grease a large casserole dish with a bit of oil, butter, or nonstick spray to prevent sticking.

Place the boneless, skinless chicken breasts in a large pot set over medium heat. Cook each side for about 6-7 minutes, or until golden brown and cooked through. Once done, transfer the cooked chicken to a board or plate and allow it to cool slightly, then shred or dice it into bite-sized pieces. I find that shredding the chicken makes for a more even texture throughout the casserole.

While the chicken is cooking, bring a large pot of salted water to a boil. Add the dried spaghetti noodles and cook until al dente, about 8-10 minutes. Drain the noodles and set them aside until ready to use.

In a large bowl, combine the shredded chicken (from Step 2), cooked spaghetti (from Step 3), condensed cream of chicken soup, diced bell pepper, smoked paprika, cayenne pepper, granulated garlic powder, and half of the grated sharp cheddar cheese (1 cup). Stir everything together until well mixed and all the spaghetti is coated in the creamy sauce. I like to toss extra cheese into the filling for an even cheesier casserole.

Transfer the combined casserole filling into the prepared casserole dish, spreading it out evenly. Sprinkle the remaining 1 cup of grated cheddar cheese all over the top. Bake in the preheated oven for 25-30 minutes or until the cheese is bubbly and golden brown.

Remove the casserole from the oven and let it rest for 5 minutes. This helps the casserole set, making it easier to serve. Before serving, sprinkle with sliced green onions for a fresh, colorful finish. For an extra kick, I sometimes add a pinch more cayenne on top before serving.