In your large pot, melt 2 tablespoons of butter over medium heat. Add the cubed chicken breast, seasoning it with salt, pepper, and garlic powder. Sauté for about 5-7 minutes until the chicken is golden brown and cooked through. Remove the chicken from the pot and set it aside.
In the same pot, add the remaining 2 tablespoons of butter. Once melted, toss in the sliced mushrooms. Sauté until they are tender and have released their moisture, about 4-5 minutes.
Sprinkle the flour over the mushrooms and stir to coat. Cook for another minute to eliminate the raw flour taste. Gradually whisk in the chicken broth and milk, ensuring there are no lumps. Bring the mixture to a simmer.
Once the sauce is thickening, add the uncooked spaghetti (or your choice of pasta) to the pot. Stir well to ensure the pasta is submerged in the sauce.
Add the cooked chicken back to the pot and stir everything together. Cover the pot and let it simmer for about 10-12 minutes or until the pasta is al dente, stirring occasionally to prevent sticking.
Once the pasta is cooked, remove the lid and stir in the Parmesan cheese until melted and creamy. Taste and adjust seasoning if necessary.
Remove the pot from heat and sprinkle the dish with fresh chopped parsley for a pop of color and freshness. Serve hot and enjoy your homemade One Pot Chicken Tetrazzini!
