Vietnamese prawn broth recipe

Ingredients
200g prawns, peeled and de-veined
2 spring onions, sliced
1 large red chilli, sliced
1l fish stock
2tbsp fish sauce
2tbsp soy sauce
100g watercress
25ml sesame oil
½tsp green peppercorns

Heat the sesame oil in a large saucepan over a moderate heat until hot. Add the chilli, then the spring onion immediately after. Stir for 1 minute, then add the fish stock. Bring to a simmer over a reduced heat and add the peppercorns. Add the prawns and allow them to simmer for 6-8 minutes until cooked. Once cooked, adjust the seasoning with the fish sauce and soy sauce. Stir in the watercress, allowing it to wilt before spooning into serving bowls.