In a small skillet, toast the rice over moderate heat, shaking the pan often, until browned, about 3 minutes. Transfer the rice to a plate and let cool completely. Once cooled, put in a spice grinder and grind to a powder.
In a small bowl, combine the lime juice with 2 tablespoons of fish sauce, 2 teaspoons to 1 tablespoon of sugar (upon taste), the minced chili, and 1 tablespoon of water. Stir until the sugar is dissolved.
In a medium sized skillet, heat the oil. Add the garlic and cook over moderately low heat, stirring a few times, until golden brown, about 1 minute. Add 1 teaspoon of sugar and cook for about 20 seconds. Add the ground pork and cook over moderately high heat, breaking up the meat finely, until no pink remains, about 3 minutes. Add 1 teaspoon of the fish sauce and season with salt and pepper. Set aside.
Remove from the heat and stir in the onion, basil, mint, cilantro and extra chili if desired. Sprinkle the pork with the rice powder and stir to mix. Transfer to a bowl and place on or near the platter with the lettuce leaves.
Let everyone spoon the pork onto the lettuce leaves and season with the dipping sauce.