- Place the fish and shellfish in a shallow pan large enough so you can arrange it without stacking. 
- Simmer the lobster shells and celery in the water for 10 minutes and remove the shells. 
- Cut the lemon into quarters, squeeze the juice into the water, and put the skins into the water; bring to a boil. 
- Add salt and pepper to taste; pour the poaching liquid over the seafood and simmer for 5 minutes. 
- Remove seafood and chill.  
- Simmer the potatoes whole in salted water until tender (ten minutes); chill. 
- Remove the stems of green beans and blanch in hot salted water for one minute and cool in cold water; let chill in refrigerator. 
- Mix all vinaigrette ingredients and shake in a bottle, leave in the bottle for transporting. 
- To assemble entrée: Line an entrée-sized plate with whole leaves of butter lettuce and shred a bit to put under the seafood to rise it up a bit and to use as salad.