In a bowl, season shredded chicken with salt, pepper, smoked paprika, and Italian seasoning.
Heat a large non-stick skillet on medium heat with oil. Sauté onion and garlic for a few seconds.
Add chicken, cauliflower, and broccoli. Stir all together. Cook for 2 minutes.
Add cream cheese, half and half, and ½ cup of cheese. Bring to a simmer until the cheese melts, then remove from the stove.
Transfer the chicken mixture to a 9x13 inch baking dish. Sprinkle the top with the rest of the cheese.
Bake in the oven for 20 minutes, until the cheese is nicely golden.
Remove and garnish with chopped parsley (optional).
Notes
Thaw and drain the vegetables well to avoid a watery casserole. Reserve some cheese for the topping to get a creamy filling with a golden, bubbly top. Let the casserole rest for a few minutes before serving. Assemble up to 24 hours ahead and refrigerate before baking.