Melt butter in a large Dutch oven over medium-high heat. Add leeks and next 4 ingredients; sauté 10 minutes or until tender. Add parsnips and next 4 ingredients; bring to a boil.
Plunge lobsters headfirst into boiling broth mixture; return to a boil. Reduce heat, and simmer 8 to 10 minutes or until lobsters are done. Remove lobsters, and cool. Remove arms and claws from lobsters; cut lobsters in half lengthwise. Remove intestinal vein, eyes, and antennae; discard.
Return broth mixture to a boil; reduce heat, and simmer, uncovered, 40 minutes or until mixture is reduced by half. Add salt and pepper to taste. Return lobster to broth, and cook until thoroughly heated.
Spoon broth mixture evenly into 6 large serving bowls; arrange lobster pieces in each. Serve with crusty bread.