Prepare the aromatics by finely mincing the lemongrass, ginger, and garlic, and slicing the chilies.

In a large wok or skillet, heat the vegetable oil and sugar over medium heat. Stir continuously until the sugar melts and turns a deep amber color.

Immediately add the pork cubes to the pan. Be careful as the caramel may splatter. Toss the pork to coat it in the caramel.

Add the minced lemongrass, ginger, garlic, and chilies to the pan. Stir-fry for about 2 minutes until the aromatics are fragrant.

Pour in the fish sauce and water. Stir well to dissolve any hardened caramel bits.

Reduce the heat to medium-low and simmer uncovered for about 15-20 minutes, stirring occasionally, until the pork is cooked through and the liquid reduces to a sticky glaze.

Season with freshly ground black pepper and give it a final toss.

Remove from heat, garnish with sliced green onions, and serve hot over steamed rice.