Step 1

Prepare the aromatics. Prepare the following, adding them to a medium bowl as you complete them: Peel and very finely chop a 2-inch piece of ginger (about 2 tablespoons). Very thinly slice 1/2 small red onion (about 1/2 cup). Very thinly slice 1 to 2 Thai chiles into rounds (use 1 for less heat).

Step 2

Marinate the aromatics. Add 1/2 cup calamansi juice and 1/4 cup of the coconut vinegar and stir to combine. Refrigerate to allow the flavors to meld while you prepare the fish.

Step 3

Cube the fish. Cut 1 pound sashimi-grade fish (discard any skin) or shrimp into 1/2-inch cubes. Place in a medium, non-reactive bowl.

Step 4

“Wash” the fish in vinegar. Add the remaining 1/2 cup coconut vinegar and stir to combine. Let sit for 2 minutes, then stir again. Strain the fish through a fine-mesh strainer into the sink, gently pressing the fish with the back of a spoon.

Step 5

Combine the fish with the aromatics. Add the fish to the ginger mixture, season with 1/2 teaspoon kosher salt and 1/4 teaspoon black pepper, and toss until completely coated.

Step 6

“Cook” the fish in vinegar. Refrigerate until the fish is “cooked” to your desired doneness, 10 minutes to 1 hour. The fish will firm up as it sits. Taste and season with more salt and pepper as needed. Stir in 2 tablespoons coconut milk to soften the sharp vinegar flavors if desired.