Warm the dashi stock in a saucepan and adjust seasoning with salt, if required. Bring to a boil over medium heat and add the prawns. Reduce heat and simmer for 1 to 2 minutes, until the prawns turn pink. Add the okra and soy sauce and remove from the heat.
Place 2 prawns in each serving bowl and ladle the soup over them. Garnish each bowl with lemon zest