Special Equipment
A large (at least 12-quart) stockpot, preferably with a perforated insert, or 2 large (at least 6-quart) pots

Fill stockpot with 6 qt. water. Add lemons, bay leaves, salt, peppercorns, and 1/2 cup Old Bay seasoning, cover, and bring to a rolling boil. Add potatoes, return to a boil, and cook 7 minutes. Add sausage and onions, return to a boil, and cook 5 minutes. Add corn, return to a boil, and cook until corn is cooked and potatoes are tender when pierced with a knife, about 5 minutes more.

For the lemon butter sauce (optional):
1/4 cup (1/2 stick) unsalted butter or margarine, melted
2 tablespoons (or more) fresh lemon juice, hot sauce (to taste; optional)

Make the lemon-butter sauce:
Melt butter in a small saucepan over medium-high heat. Transfer to a medium bowl and stir in lemon juice and hot sauce, if using. Taste and add more lemon juice, if needed. Cover and let sit in a warm place.

Add shrimp and cook (no need to return to a boil), stirring gently, until shrimp turn pink, about 3 minutes. Remove insert or drain through a very large colander.

Serve the shrimp boil:
Serve shrimp boil on a newspaper-lined table or large platters. Serve with sauces alongside, if desired.

Serve with lemon sauce and Cocktail Sauce.

Cooks' Note

If you can't find small new potatoes, cut larger potatoes into 1 1/2" chunks.