Break the chard into separate stems, remove any hollow or discoloured pieces and peel away any stringy lengths, then chop into 5cm (2in) pieces. Trim and chop the runner beans also into 5cm (2in) lengths.
Heat the oven to Gas 4, 180ºC, 350ºF. Lightly brush a baking tray with olive oil and place two trout fillets on top of one another, overlapping each end so that they cross and form an ‘X'.
Steam the potatoes for 15 minutes or until they are soft. Place the trout fillets in the top of the oven and cook for 8-10 minutes. Place the butter, shallot and garlic in a small pan and cook over a low heat for 5 minutes.
Remove the potatoes from the steamer and keep warm. Place the chard and beans in the steamer and cook for 5 minutes. Add the parsley and lemon juice to the shallot pan and allow to a simmer.
Place the potatoes on a plate, top with the steamed chard and beans, followed by the brown trout. Spoon over the lemon and parsley sauce and add a twist of black pepper.