Shrimp Butter
1 small white onion, finely minced (about 1/2 cup)
1 1/2 pounds large shrimp, shell on (see recipe note)
2 teaspoons kosher salt, plus more for salting the water
1 pound unsalted butter, at room temperature
2 teaspoons lemon zest
2 tablespoons lemon juice
1 tablespoon Worcestershire sauce
1/4 cup finely chopped fresh parsley
1/4 cup finely chopped fresh dill
1/2 teaspoon freshly ground black pepper
1/2 teaspoon celery seed
Soak the onion:
In a small bowl, add the chopped onion and cover with cold water and an ice cube. Allow onion to sit in water for at least 5 minutes to let the flavor mellow. Afterward, drain from water, pat dry with a paper towel, and set aside.
Poach the shrimp:
Meanwhile, fill a medium bowl with ice water for shocking the cooked shrimp. Set aside.
Fill a medium saucepan with salted water and bring to a boil over high heat. Lower the heat to a simmer and add the shrimp. Cook until shrimp are completely pink and firm to the touch, 5-7 minutes.
Transfer to the bowl of ice water and let sit until cool enough to handle. Peel and, if necessary, devein. Then pat dry and transfer to a cutting board.
Chop the shrimp:
Chop the shrimp very finely until it’s nearly a paste.
Beat the butter:
In a large bowl, beat the butter with a wooden spoon until smooth.
Add the remaining ingredients:
Add the chopped shrimp and remaining 1 teaspoon salt, lemon zest and juice, Worcestershire sauce, herbs, pepper, and celery seed.
Mash with the back of a fork (or continue using the wooden spoon) until all of the ingredients are well distributed.
Serve:
Serve immediately with saltines (or any light, crisp cracker), or refrigerate in an airtight container for up to 1 week. Let come to room temperature at least 30 minutes before serving; when pliable, re-beat until spreadable and creamy.
Shrimp butter can be made ahead and frozen for up to 1 month. To store, spoon the butter onto a sheet of plastic wrap and roll into a log.