Cut carrots and celery into 1/2-inch thick slices. Peel and cut potatoes into 3/4-inch cubes.
Place in wide saucepan along with leek/onion, salt and water; bring to boil. Cover and reduce heat to medium; simmer for 10 minutes.
Meanwhile, in bowl, lightly beat egg; mix in bread crumbs, onion, garlic, parsley, dill, salt, pepper and cayenne. Add ground lamb and mix well. Form into 1-inch (2.5 cm) balls. Spread flour on plate; roll each ball in flour.
In nonstick skillet, heat oil over medium-high heat; brown meatballs.
Add meatballs to vegetables; simmer, covered, for 20 minutes. Remove with slotted spoon when cooked through.
Meanwhile - in bowl, whisk eggs with lemon juice; whisk in the cooking liquid. Pour back into saucepan; cook, stirring constantly and being careful not to boil, until thick enough to coat back of spoon, about 3 minutes.
To serve plate meatballs and vegetables, pour sauce over meatballs and serve with rice and perhaps a salad. Garnish with parsley or dill.