Try this delicious recipe from Marion's Thailand
To make sweet and sour sauce, heat sugar, vinegar and fish sauce in a small saucepan over high heat until the sugar dissolves. Set aside to cool, then stir in the coriander.
Use a sharp knife to remove the skin from the pork belly. Discard the skin, cut the pork belly into 3 cm cubes and place in a large bowl.
Use a mortar and pestle to pound coriander roots, garlic, peppercorns and salt to a rough paste. Add paste to the pork belly along with the soy sauce, fish sauce and sugar. At this stage the pork can be left to marinate for up to 12 hours if you’re not serving straight away.
When ready to serve, heat 10 cm of vegetable oil in a wok or large heavy-based saucepan to 180°C. Toss the pork belly in flour to coat, then carefully drop the pork, in batches, into the oil and cook for about 5 minutes or until golden brown. Remove with a slotted spoon and drain on paper towel.
To serve, place fried pork onto a serving plate and pour over the sweet and sour sauce