In a large pot, combine wild rice, water, and salt. Bring a boil and simmer for about 45 minutes, until rice is cooked through and water is absorbed. Set aside.
In a large sauté pan or dutch oven, melt butter over medium heat. Add the shiitake and portobello mushrooms and cook for about 10 minutes, stirring regularly, until mushrooms are softened and edges are browned.
Add the chinese sausage or ground pork and continue cooking for 6-7 minutes, until meat is cooked through. Stir in the rice vinegar, water chestnuts, soy sauce, and wild rice. Cook for another 5-10 minutes and then serve, topped with chopped green onions.