Boil the chicken stock, then add the wild rice, the brown rice and the bay leaves. Simmer until the wild rice starts to "break" and the brown rice is cooked. Most of the broth should now be absorbed. While this is simmering, melt the butter in a skillet. Add the onion and cook until tender. Add the ground beef and cook until there in no pink left. Add the mushrooms, water chestnuts, soy sauce, and curry powder and stir to mix. When the rice mixture has absorbed most of the broth, add the beef mixture and mix thouroughly. Put in a 14"x9" casserole, removing the bay leaves. Top with cheese and bake in the oven at 350 for approximately 20 minutes so the cheese can melt and lightly brown.