In a large skillet (the largest you have) melt 4 tablespoons butter over medium heat.
Add the onion, garlic, red pepper and mushrooms and saute for about 8 to 10 minutes, until the mushrooms release their liquid and it is almost evaporated.
Sprinkle with flour and continue cooking for a minute or two.
Slowly add the chicken broth, milk, salt and pepper and bring to a boil.
Reduce the heat and simmer for a few minutes until thickened.
Remove from heat, add the nutmeg and the cheese a handful at a time, stirring until melted.
Stir in the thawed broccoli, cooked pasta and cooked chicken.
If your skillet is not large enough, mix in a large bowl.
Transfer to a lightly greased 9 x 13" casserole dish.
In a small bowl melt the remaining 2 tablespoons butter in the microwave.
Stir in the panko and the Parmesan Cheese.
Sprinkle over the top of the casserole.
Bake at 350 degrees for 30-40 minutes until bubbly and the top is browned.
Recipe by Sunflower Supper Club at https://sunflowersupperclub.com/chicken-and-broccoli-pasta/