01 -
Bring a large pot of water to a boil. Meanwhile, fill a medium bowl halfway with ice and cold water to make an ice bath. Line a baking sheet with a double layer of paper towels.
02 -
Add the raw large shrimp to the boiling water. Boil until the shrimp are pink and just cooked through, about 2 minutes for fresh and 3 1/2 minutes for frozen. Drain, then transfer the shrimp to the ice bath. Once chilled, drain the shrimp again and discard any remaining ice cubes. Transfer the shrimp to the paper towels and arrange in a single layer to dry.
03 -
Juice the lime until you have 2 tablespoons. Finely chop the celery stalk (about 1/2 cup) and shallot (about 1/4 cup). Pick the leaves from the cilantro sprigs and finely chop (2 tablespoons). Halve and pit the avocado. Cut one half of the avocado into 1/3- to 1/4-inch pieces.
04 -
Scoop out the flesh from the remaining avocado half into a medium bowl. Add the mayonnaise and, using a whisk, mash the avocado, then whisk until mostly smooth. Add the lime juice and kosher salt, and whisk to combine. Add the celery, shallot, and cilantro, then mix until well combined.
05 -
Add the shrimp and remaining avocado pieces to the bowl, then toss until evenly coated, doing your best to keep the avocado pieces intact. Taste and season with additional kosher salt as needed. Serve on toasted bread, in a hot dog bun, or on salad greens if desired.