1. Season chicken pieces with salt and pepper.
2. In a large brasier, melt the butter and olive oil over medium-high heat.
3. Add the seasoned chicken pieces and sauté for about 3 minutes, until the chicken turns opaque.
4. Add the sliced mushrooms and cook for an additional 2 minutes, or until mushrooms are limp.
5. Add the garlic, herbs and cayenne and stir for about 20 seconds; do not let garlic brown.
6. Stir in the flour and cook for about 1 minute, stirring constantly.
7. Add the milk a few cups at a time, whisking vigorously to incorporate. Milk should incorporate with no flour lumps.
8. Bring to a simmer and whisk occasionally until the sauce is thickened, about 8-10 minutes.
9. Remove from the heat and place in a shallow pan to cool in the refrigerator. NOTE: Sauce can be made up to two days in advance and kept covered and refrigerated.
10. Meanwhile, bring a large pot of water to a boil and cook the penne pasta according to package directions. Drain well.
11. In a very large bowl, mix together the pasta and cooled sauce.
12. Fold in the grapes, chopped artichoke hearts, green onions, 2 cups of the Parmesan cheese and the grated mozzarella cheese until well combined.
13. Place the mixture into a 2-inch full size hotel pan.
14. Sprinkle with the remaining 1 cup of Parmesan cheese and bake in a 375 F conventional or standard deck oven for about 50-60 minutes, (350 F in a convection oven – adjusting time as needed) or until pasta is an internal temperature of 160-165 F, the sides are slightly bubbling and the top is golden brown.