Preheat the oven to 350 degrees fahrenheit.
In a large nonstick frying pan over medium heat warm the olive oil and start cooking the diced mushrooms and onion seasoning them with salt and pepper to taste.
Add the broccoli, red bell pepper, cauliflower florets, and vegetable broth mixing them until combined. Cook for another 3 minutes or until the broccoli is crisp-tender and bright green.
Stir in the shredded chicken and cook for about 5 minutes.
Meanwhile in a large blender, place the soaked cashews, water, minced garlic, lemon juice, diced onion, nutritional yeast, salt, dried rosemary and black pepper to taste.
Puree everything until creamy.
Pour the sauce in the frying pan and mix until everything is combined.
Transfer the whole thing into a 9x13-inch pan and place it in the oven for about 20 to 25 minutes.
Let it cool slightly and serve to enjoy.