1 small serrano chile, stemmed, seeded, and minced
2 tablespoons (30ml) rice vinegar
1/4 teaspoon kosher salt; for table salt, use a pinch
1 small shallot (1 ounce; 28g), finely chopped
1 medium celery stalk (1 3/4 ounces; 50g), finely chopped
1/2 cup mayonnaise (3 1/2 ounces; 100g)
1/4 cup crème fraîche or sour cream (2 ounces; 60g)
2 tablespoons finely chopped fresh cilantro leaves and tender stems
1/2 teaspoon instant dashi powder, such as Ajinomoto
1 pound (454g) flake-style surimi seafood (imitation crab), patted dry (see notes)
In a medium bowl, stir together chile, vinegar, and salt. Let stand 10 minutes.
Meanwhile, place shallot in a fine-mesh sieve and rinse under hot water. Drain thoroughly.
Add rinsed shallot, celery, mayonnaise, crème fraîche, cilantro, and dashi powder to vinegar mixture, stirring with a silicone spatula until dashi powder dissolves.
Add surimi, and gently toss to combine.
Serve immediately.