Step 1: Prepare the Shrimp Poaching Liquid : In a large pot, combine water, lemon halves, garlic, bay leaf, salt, peppercorns, and Old Bay seasoning. Bring to a gentle boil, then reduce the heat to medium and simmer for 5 minutes to infuse the flavors.
Step 2: Cook the Shrimp : Add the shrimp to the simmering liquid and cook for 2–3 minutes, just until they turn pink and opaque. Immediately remove the shrimp with a slotted spoon. Transfer them to a bowl of ice water to stop the cooking process and keep them firm and juicy. Let the shrimp chill for 5 minutes, then drain and pat dry with paper towels.
Step 3: Make the Tangy Cocktail Sauce : In a small bowl, combine ketchup, horseradish, lemon juice, Worcestershire sauce, and hot sauce. Mix well until smooth. Taste and adjust seasoning — add more horseradish for spice or more ketchup for sweetness. Chill the sauce for at least 20–30 minutes for the flavors to meld.
Step 4: Chill and Assemble : Arrange the shrimp in a serving dish or around the rim of cocktail glasses. Place a small bowl of cocktail sauce in the center. Garnish with lemon wedges and parsley sprigs for presentation. Serve cold and enjoy!