Ingredients

2 pounds large shrimp (16-20 count), peel on

2 large carrots, scrubbed but not peeled, cut into thirds

1 stalk celery with leaves, cut into thirds

4 sprigs thyme

1/2 teaspoon whole peppercorns

1 tablespoon kosher salt

2 lemons

3/4 cup ketchup

1 tablespoon fresh lemon juice

1 to 3 tablespoons fresh horseradish or prepared horseradish

1/2 teaspoon kosher salt

1/2 teaspoon freshly ground black pepper

1/2 teaspoon hot sauce, such as Tabasco (optional)

Preparation

Shrimp: Cover a rimmed baking sheet with ice (to later cool down shrimp). In a large stockpot combine 12 cups water, carrot, celery, thyme, 1 tablespoon salt, and peppercorns. Cut one lemon in half; squeeze half the juice into the water and add the rind. Cut remaining 1 1/2 lemons into small wedges for serving; set aside.

Bring water to a boil. Add shrimp, cover; remove from heat. Let stand until shrimp are bright pink and curled; 3 to 5 minutes. Drain and transfer to prepared tray of ice to cool completely. Once cool, shrimp can be refrigerated in an airtight container up to 2 days.

Cocktail Sauce: Meanwhile, whisk together all ingredients until combined. (Cocktail sauce can be made ahead; refrigerate in an airtight container up to 1 week.)

To Serve: Peel shrimp, leaving tails intact if desired. Using a paring knife, make a shallow cut along backs of shrimp to remove vein. Arrange shrimp neatly on a platter, shingling them slightly to make a pattern, and serve chilled with cocktail sauce and reserved lemon wedges on the side.