Thai Lettuce Cups (Larb Gai)

INGREDIENTS
2 tsp cornstarch / corn flour
2 tbsp water
2½ tbsp lime juice (1 to 2 limes)
1½ tbsp fish sauce
2 tsp brown sugar
2 tbsp peanut oil
1 tbsp fresh ginger, grated
2 garlic cloves, minced
1 lemon grass stalk, white and very pale green part only, finely chopped
2 birds eye chilli, minced
1lb/500g lean ground chicken
½ red onion, cut into 4 wedges then finely sliced
⅓ cup cilantro/coriander leaves
.
DIRECTIONS:
1 Mix water and cornstarch in a small bowl. Add lime juice, fish sauce and sugar and mix to combine.
2 Heat peanut oil in a wok over medium high heat. Add ginger, garlic, lemongrass and chilli and sauté for 45 seconds to 1 minute until fragrant.
3 Turn up the heat to high. And cook chicken, breaking up the mince into small pieces.
4 Once the chicken turns white, add the sauce from Step 1. Cook for 45 seconds to 1 minute to coat the chicken and for the sauce to thicken.
5 Remove wok from heat. Stir through onion, coriander/cilantro and mint.
Spoon into lettuce cups and serve. Garnish with extra mint, coriander/cilantro leaves and peanuts, if using.