Place the trout in a large frying pan or a heavy-based roasting tin.
Now sprinkle a little salt over them and throw in the peppercorns. Next add the bay leaves, one in between each trout. Lay onion rings over the top, cut half the lemon into slices and arrange them here and there. Add the thyme and sprinkle a tablespoon of chopped parsley over everything. Finally add the wine and enough cold water just to cover the fish. Bring it to the boil on top of the stove and let it simmer gently, uncovered, for 6 minutes if the trout are fresh or 20 minutes if they are frozen.
Mix the remaining parsley and the chives with the butter in a small basin, then divide the mixture into four portions. When the trout are ready, carefully lift them out with a fish slice, allowing each one to drain for a few seconds, and serve with the parsley butter and the other half of the lemon cut into wedges.