Shrimp Butter

Soak the onion: In a small bowl, add the chopped onion and cover with cold water and an ice cube. Let sit for at least 5 minutes to let the flavor mellow. Drain the onions, 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 the shrimp are completely pink and firm to the touch, 5 to 7 minutes. Use a slotted spoon or spider to transfer the shrimp 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 with a knife or in a food processor 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 shrimp, salt, lemon zest and juice, Worcestershire sauce, parsley, dill, black 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. Taste and adjust the seasoning as desired.

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 softened, 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. Let thaw in the refrigerator, then bring to room temperature and re-beat until smooth.