Boil and stir 1 minute. Remove from heat. Quickly stir several tablespoons of the hot mixture into egg yolk. Blend egg mixture into remaining hot mixture. Taste and add salt and pepper if desired.
Fill shells with lobster mixture.
Bake 5 - 8 minutes. Bring a medium pot of salted water to a boil. Add the potatoes and cook over medium heat until the potatoes are just done, about 8 minutes. Remove with a slotted spoon, rise, drain, and toss with half of the dressing in a large bowl. Place the same pot of water used to cook the potatoes over high heat.