The day before you make the soup, make the chilli paste. Place all ingredients in a blender or food processor and blend to a smooth paste. Transfer to a saucepan and bring to a simmer. Cook off excess liquid, then store in a plastic container in the refrigerator.
To make the soup, place the shallots in a saucepan and cook 2-3 minutes until they give up their liquid. Add shredded chicken and 2 tablespoons of the chilli paste. Cook a further 3 minutes then add the rice wine to deglaze. Add the chicken stock and bring to a simmer.
Add the rice noodles and cook 2 more minutes. Add the sliced shallots, leek and coriander and serve at once, with soy sauce and chilli flakes on the side.