Bring a large pot of water up to a boil.

Add sliced fish into the pot and cook for 2-3 minutes.

Drain the sliced fish and rinse under cold water.

Transfer the cooked sliced fish to a basin or bowl filled with ice water and chill in the fridge for 1 hour.

In a small saucepan, heat up a pan over medium heat and toast Sichuan peppercorn seeds, about 1-2 minutes, or until just fragrant.

Remove Sichuan peppercorns from heat. Let cool, transfer to a spice grinder and grind into a powder. Set aside.

Using the same pan, add in 1 teaspoon of sesame oil and add in minced garlic, sauteing until slightly brown, about 1 minute.

Transfer the sauteed garlic to a small bowl and stir in soy sauce, rice vinegar, sesame oil, sugar, ground Sichuan peppercorn, chili oil (if using), cilantro, green onion, sesame seeds and red chili (if using). Mix well.

Remove the fish from the fridge, drain well and pat dry with paper towel.

Add the fish to the sauce and coat thoroughly with the sauce.

Chill until ready to serve.