Court bouillon loosely translates as 'briefly boiled liquid' and is a quickly-cooked broth used for poaching other foods, commonly fish or seafood. Poaching is a gentle method of cooking. The fish is submerged in liquid and cooked over low heat or covered and oven-poached at 180°C. The liquid barely simmers throughout the process which prevents the fish from breaking up.
To make the court bouillon simply put all the ingredients in a large enough pan and simmer for 15 minutes.
Place the salmon fillets or whole salmon in a large saucepan or fish kettle and cover with the court bouillon, add some water to ensure the fish is just submerged. Bring slowly to the a boil. Reduce the heat and cook over low heat so that the liquid just blips.
Cover and cook the fillets or 5 minutes (15 minutes if using a whole salmon) until the fish has lost its translucency and is pale pink in colour. Turn the heat off and leave for 5 minutes. Lift the fish from the court bouillon and pat dry with kitchen paper.
Make sure the fish is cool and break the flesh into chunky flakes, removing any bones.
Cook the potatoes in boiling salted water with the sprigs of mint until tender. Drain and leave them to cool. Slice into halves or quarters, depending on size.
To make the dressing, mix everything together, and season well. Stir half into the potatoes and add the sliced spring onions.
Scatter the pea shoots on a large serving platter and arrange the potatoes, salmon and prawns on top.
Spoon over the some of the remaining dressing and place the rest in a bowl to serve separately. Garnish with extra dill and remaining chopped gherkins.