Sauté the leeks, lemongrass and onion in the butter in a heavy saucepan until tender. Do not allow to colour. Add the diced potatoes and stir to mix. Pour in the stock; bring to the boil and cook, covered, for about 15 minutes. Add the peas and cook for a further 5 minutes. Add the milk, lime juice, season to taste and liquidise the soup in a food processor until smooth. Pass through a fine sieve and season to taste.
Aloe vera Jelly:
Bring to the boil the fish stock, aloe vera & ginger and cook for 6-8 minutes. Add the agar-agar and cook for 5 minutes more and remove from the heat. Soften the gelatine leaves in a little cold water for 1 minute and add them to the aloe vera stock. Season with salt and pass through a fine sieve. Pour onto a large, flat tray to about 1cm thickness. Allow to set in the fridge.
Heat the milk to between 65-70 degrees ºC. Slowly poach the cod fillets over a very gentle flame for 5 minutes until just cooked and translucent. (The milk should never be over 70 degrees so that the gelatine in the fish does not coagulate and dry out.)
Carefully remove the fish fillets and divide between 4 large bowls. Cut squares of Aloe vera jelly and place them on top of the fish. Garnish with Samphire (Salicornia) and fresh peas and serve with the warm pea & lemongrass soup.
A spoonful of caviar is entirely optional but it finishes the dish perfectly!