Heat the oil in a heavy pan over medium heat. Add the shallot, garlic, and jalapeño – saute until fragrant, about 2 minutes. Turn the heat to high and add the pork and the fish sauce – stir fry for a few minutes until the pork is no longer pink. With the heat very high, add the sugar and water and stir once – then let the pork caramelize by not stirring it for about 1 minute. Repeat this process until the pork is nice and golden brown.
Toss everything together in a medium bowl.
Warm the tortillas quickly in a skillet with a little bit of oil. Arrange the pork between 6 tortillas and top with the salsa and the chili sauce.