Cook pasta: Fill a large pot with water and bring to a boil. Sprinkle generously with salt. Add the pasta and cook for 8-10 minutes or according to package instructions so that the pasta is al dente. When done, rinse the pasta with cool water and drain, then set aside.
Saute vegetables: Heat 1/2 tablespoon of olive oil over medium heat in a large skillet. Add the onion, saute for 2 minutes, then add the mushrooms, season with salt and pepper and cook for another 5 minutes or until tender. Transfer to a bowl and set aside.
Cook chicken: Heat remaining 1/2 tablespoon of olive oil over medium heat. When warm, add the chicken and salt and pepper to taste. Cook for about 5 minutes, or until the chicken is no longer pink. Transfer to a bowl (with the mushrooms is fine) and set aside.
Make cheese sauce: Wipe skillet clean and melt the butter over medium heat. As it starts to melt, whisk in the flour. Then whisk in the milk, chicken broth, Italian seasoning, salt and pepper. Increase heat to medium-high and bring to a boil. Continue whisking frequently for 4-5 minutes or until mixture becomes thick. Then remove from heat and stir in both cheeses. Taste and add any salt or seasonings to taste.
Making the mac and cheese: Cut sun dried tomatoes into small pieces. To the skillet with the cheese sauce, fold in the sun dried tomatoes, cooked macaroni, spinach, chicken, mushrooms and onions and mix until everything is well combined. Sprinkle with freshly cracked black pepper to serve!