In a bowl, combine the oyster sauce, fish sauce, sugar, water, and shrimp paste. Stir well until the sugar dissolves.

Use a mortar and pestle to pound the garlic until chunky. Remove all but about 1 clove's worth and add in the white peppercorns and chopped cilantro stems, then pound into a paste.

Pat the shrimp dry with paper towels to ensure they sear properly.

In a hot wok, add enough oil to coat the bottom. Once it's shimmering, add the shrimp in a single layer. Sear until they're halfway cooked and slightly browned—about 2-3 minutes. Flip and cook the other side until done, then remove and set aside.

Let the pan cool slightly (about 30 seconds) and add the chunky garlic back in. Return the heat to medium-low, sautéing for about 2 minutes until softened and edges turn golden. Add the herb paste and sauté for another 15-20 seconds.

Increase the heat to medium, return the cooked shrimp along with any collected juices, and pour in the sauce mixture. Toss everything together for about 30 seconds, mixing well and allowing the sauce to reduce slightly.

Plate the shrimp beautifully and garnish with chopped cilantro, green onions, or fried garlic as desired. Serve hot over jasmine rice.