First, take a large pot and to it, add the ground chicken, enough water, the lemongrass leaves, rice wine vinegar and 2-3 garlic cloves. Cover and allow to simmer on a gentle heat till the chicken is cooked.
Next, drain off the water, remove the lemongrass leaves. Keep the chicken and garlic cloves aside.
In a wok, heat the oil and allow it to get hot. Add in the garlic you saved from boiling the chicken, the thinly sliced ginger, mushrooms, onions and swish around for about 30 seconds before adding the soy sauce and stir-frying.
Once the soy sauce is in, stir-fry for about minute more
Next, add in the chicken and cashewnuts and stir-fry; followed by the the tomatoes, bell peppers, crushed chilli flakes, sugar and salt. Allow to cook for about 2 minutes more.
Allow the chicken to cool a little before placing on washed and dried lettuce leaves. Roll up and enjoy! I actually prefer this as a cold salad, and chilled by chicken in the fridge before wrapping it in lettuce. But hot chicken stir-fry+ice cold lettuce also works!