Preheat oven to 375 degrees. Cook chicken breasts in a slow cooker 3 hours on high or 6 hours on low. I always add a little chicken broth and salt and pepper, but you can use water instead. Remove from the slow cooker and shred. My family prefers chicken breasts, but you can use thighs or a whole chicken too. Or, skip preparing the chicken and use a rotisserie chicken instead to save time.
Cook the fresh broccoli or microwave the steam bags of broccoli and drain.
In a saucepan, add butter, heavy whipping cream, garlic, and 1/2 of the Italian seasoning. Add softened cream cheese and stir with a whisk until thoroughly combined and cook over low medium heat until the sauce is smooth.
Add cheeses stirring continually reserving 1/4 cup of cheddar cheese 1/8 cup of the other cheeses for the topping.
Grease a 9 X 13 casserole dish and layer the shredded chicken first.
Add the steamed broccoli on top of the chicken.
Remove saucepan with the cheese sauce from the stove and pour on top of the broccoli and shredded chicken making sure that it is completely covered.
Sprinkle the reserved cheese on top of the casserole along with parsley, paprika, and the remaining Italian seasoning.
Bake in a 375-degree oven for 30 minutes.