Wash the trout and dab dry. Clean and wash spring onion and cut into thin rings. Peel garlic and chop finely. Mix butter, spring onion, garlic and herbs. Season with salt and pepper.
Stuff trout with it. Close the opening with a wooden skewer. Season fish outside with salt and pepper, rub with oil. Roast in the pan or under the grill in the oven while turning for about 15 minutes.
Bacon and potato salad, for example, is delicious with it.