First, get the vermicelli in a bowl of water to soak until soften.
Meanwhile, let's start with the dressing. Chop the garlic and chillies then add to a bowl. Add the sugar, fish sauce and lime juice then stir until the sugar is dissolved. Keep tasting the dressing, be mindful that this will be diluted when poured over the salad anyways so it could taste quite strong as is. When you're happy with the balance of flavour, set it aside.
Season the minced pork with a ½ tsp of fish sauce. In a hot saucepan, add the slight stock then the pork mince immediately. Stir well to avoid the mince clumping up.
After the pork is cooked, this should only take 2-3 minutes, turn off the heat. Then add the soaked vermicelli noodles. Again, stirring to avoid the noodles clumping together. The residual heat from the pan will be enough to cook the noodles.
Season the salad by adding the dressing we made earlier. Then add the thinly sliced onions, tomatoes and celery.