1 (2-inch) knob fresh ginger, peeled and thinly sliced
2 sprigs flat-leaf parsley
Fresh juice of 1 lemon
1/2 C ketchup
1/2 C chili sauce
2 TBSP horseradish, plus more to taste
1 TBSP fresh juice from 1 lemon
Kosher salt and freshly ground black pepper
In a medium pot, combine 2 quarts water with celery, onion, garlic, parsley, lemon juice, 2 tablespoons salt, and the 2lb of shrimp. Set range top to medium-high heat and cook, stirring occasionally, until temperature reaches 170°F on an instant-read thermometer and shrimp are just cooked through; adjust heat to make sure temperature does not go over 170°F.
Using a slotted spoon, transfer shrimp to zipper-lock bags, making sure not to crowd too many shrimp into each bag. Seal bags, removing as much air as possible, and submerge in ice water, moving shrimp around in each bag, until cooled. Transfer zipper-lock bags to refrigerator until shrimp are thoroughly chilled, at least 30 minutes. Peel and devein shrimp.
In a medium bowl, whisk the ketchup, chili sauce, horseradish, and lemon juice together. Season with salt and pepper. Serve with chilled shrimp.