With a cleaver, chop chicken legs into 2" pieces. Chop one onion into medium dice and set aside; peel the second onion.
Heat oil in a large soup pot. When oil is shimmering, add half the chicken pieces in a single layer. Cook over medium-high heat, turning occasionally, until browned on all sides. Remove to a bowl and repeat with remaining pieces.
Add diced onion to pot and saute until soft and beginning to color. Return chicken (and any accumulated juices) to pot. Season with salt and pepper. Add boiling water, carrots, parsnip, celery, dill, parsley, bay leaves and reserved whole onion. Cover and cook at a bare simmer one hour, skimming off and discarding any grey foam which rises to the surface.
Strain and use as a cooking base, or a soup base. (To serve as a soup, simmer sliced carrots in broth until tender. Add egg noodles and cook until al dente, then serve.).