Mix the sauce ingredients (soy, oyster, wine, sesame oil, and sugar) at home and put in a container for the trip. At camp, break out a cast iron dutch oven or other pot that can handle high heat. Add a bit of oil to the pot and, once hot, introduce the chicken and sausage and fry until lightly browned. Toss in the garlic, let soften and become fragrant, then add the rice, mushrooms, half of the prepared sauce, and the water. Add salt and pepper to your liking. Let the liquid come to a boil then bring down the heat from a burner to low, if using, or move the pot to cooler part of a fire, cover and let simmer lightly for 18-20 minutes. Remove from heat, let rest with lid on for five minutes, then remove the lid, mix and fluff with a fork. Serve with chopped green onions, the rest of the prepared sauce, and chili flakes.