Cut walleye fillets into cube size, allowing for ease of cooking and eating. Spray the bottom of a frying pan, skillet, or electric wok with non-stick spray. Combine soy sauce to taste, fish, water chestnuts, and a splash of white wine in pan. Cover and simmer for 5 minutes at medium heat. The fish will be done when they are a similar color to the water chestnuts. Pour in bag of frozen vegetables, cover pan again and simmer for 5 more minutes. Add stir-fry sauce, letting it sit for 5 minutes to permeate food. Add to bed of rice or chow mien noodles. Garnish with cashews (optional).