Preheat oven to 350 degrees F (175 degrees C).In a large saucepan over medium-low heat, combine 1 1/4 cupsbroth, yeast extract, lentils and barley. Simmer for 30 minutes.Meanwhile, in a medium saucepan combine remaining 3/4 cupbroth, carrot, onion and walnuts; cook until tender, about 15minutes.Meanwhile, bring a large pot of salted water to a boil. Add potatoesand cook until tender but still firm, about 15 minutes. Drain andmash.Combine flour and water and stir into carrot mixture; simmer untilthickened. Combine carrot mixture with lentil mixture and seasonwith salt and pepper. Pour mixture into a 2 quart casserole dish.Spoon mashed potatoes over lentil mixture.Bake in preheated oven until lightly browned on top, about 30minutes.