1. Melt the butter in a frying pan.
2. Dice the onion and fry until soft.
3. Core and dice the apple, and add to the onion. Fry for 1 minute.
4. Add the lemon juice, lemon thyme, parsley and a sprinkling of pepper, and mix well.
5. Fill the cavity of each trout with the stuffing and secure the opening with wooden cocktail sticks.
6. Brush the skin of the fish with olive oil and grill or bake 5-8 minutes each side until cooked (the eye will turn white and the flesh will flake).
7. Serve with low-ox salad or vegetable risotto.