Combine the teriyaki sauce, mustard, sour cream, water, minced garlic, lemon juice, honey (if you want sweeter stew), salt and pepper in a bowl.
Preheat the oven to 360 degrees F. Pour the vegetable oil into a baking dish and place chicken, cauliflower florets and onions in the baking dish. Then pour the combined sauce over it and mix well.
Put the baking dish in the oven and bake until chicken and cauliflower are tender and desired thickness, about an hour and half, stirring occasionally. If the stew is too thick add some water. Serve the teriyaki chicken stew with rice or bread.