Preheat oven to 375 degrees.
In a large bowl, mix condensed soup, sour cream, garlic, and salt. Add cauliflower, mixed veggies, and mushrooms, and stir to coat. Set aside.
Lay a large piece of heavy-duty foil on a baking sheet and spray with nonstick spray. Season chicken with salt, black pepper, and any additional spices you like. Place chicken in center of the foil, and top with veggie mixture.
Place another large piece of foil on top. Fold together and seal all four edges of the two foil pieces, forming a well-sealed packet.
Place baking sheet in the oven and bake for about 1 hour, until chicken is cooked through.