Place lentils and water in a saucepan, and bring to a boil. Cover, reduce heat to low, and simmer until tender, about 30 minutes. Drain.
In a large bowl, mix together the cooked lentils, milk, wheat and barley cereal, eggs and walnuts. Season with onion soup mix and poultry seasoning. Mix well using your hands, as the mixture will be very thick. Let stand for 30 minutes, or refrigerate overnight.
Heat oil in a large skillet over medium heat. Use an ice cream scoop to portion out balls of the lentil mixture. Drop the scoops into bread crumbs, and coat while flattening into patties. Fry burgers in the hot skillet until nicely browned on both sides, about 5 minutes per side, depending on the thickness of the patties.