Prep Chicken:
Preheat oven to 375°F. Slice each chicken breast in half lengthwise for thinner cutlets. Heat olive oil in a deep skillet over medium heat. Cook chicken cutlets 3–4 minutes per side until golden brown and fully cooked. Remove and let rest. Chop into bite-sized pieces once cooled.

Cook Spaghetti:
In a large pot, bring salted water to a boil. Add spaghetti and cook until just al dente (firm to the bite). Drain and set aside.

Make the Creamy Sauce:
In the same skillet, melt butter over medium-high heat. Add diced onion and garlic. Sauté for 3–4 minutes until translucent.
Sprinkle in flour and stir to coat. Cook 2–3 minutes to form a roux.
Gradually pour in chicken broth while whisking until smooth.
Add salt, pepper, Italian seasoning, and half of each cheese (½ cup cheddar, ½ cup mozzarella).
Stir in heavy cream until the sauce is creamy and smooth.

Assemble Casserole:
Add chopped chicken, drained Rotel, and cooked spaghetti to the sauce. Mix until well combined.

Bake It:
Transfer mixture to a greased 9×13” casserole dish. Top with remaining cheese.
Bake for 25 minutes until cheese is melted and bubbling. Broil for 2–3 minutes for a golden top if desired.

Serve:
Let sit for 5–10 minutes before serving to thicken slightly and hold its shape.