Mix the marinade: combine Fish Sauce, Brown Sugar, Lemongrass, Lime Juice and Garlic in a bowl. Add the Boneless Chicken Thighs and toss to coat. Set aside to marinate for 15 minutes while you prepare everything else (or overnight).
Make the peanut sauce: mix Natural Peanut Butter, Hoisin Sauce, White Vinegar, Milk, a little Garlic, Brown Sugar and a pinch of Kosher Salt together in a small bowl until combined; add Chilli Paste to taste and use extra milk to adjust the consistency so it's not too thick.
Place the Dried Vermicelli Noodles in a bowl and cover with hot water for 2 minutes, then drain very well and let cool (or follow packet instructions, if different).
Heat the Canola Oil in a large non-stick pan over high heat until very hot. Add half the Boneless Chicken Thighs (leave residual marinade in the bowl) and cook for about 3 minutes, stirring constantly, until lightly caramelised. Remove from the pan and spread out on a plate to cool before using. Repeat with the remaining chicken.
Fill a large bowl with warm water (the bowl doesn't need to fit the whole rice paper at once).
Submerge a Round Rice Paper in the water for about 2 seconds (if your bowl isn't large enough to fit the whole sheet, rotate it and count 2 seconds for each section you submerge), then place the smooth side down on a cutting board.
Place the stuffing just beneath the middle in a symmetrical stack for easier rolling: sprinkle some Coriander/Cilantro Leaves, top with one-tenth of the cooked Boneless Chicken Thighs, then add Carrot, Green Cabbage, Red Cabbage, a generous amount of Mint Leaves and the Dried Vermicelli Noodles last to weigh everything down (you can wrap around your hand to bundle into a neat shape).
Fold the lower part of the rice paper up over the stuffing, fold the sides in, and roll to enclose the filling, making it fairly firm so it seals to itself. Don't worry if it's a bit wonky — it will still taste fabulous.
Transfer the rolls to a serving plate (don't stack them or they may stick). Serve with the peanut dipping sauce; optionally cut rolls in half and stand upright for a pretty presentation.
