- Preheat your oven to 230°C.
- Lay a piece of baking paper, or tin foil, over another, long side of the paper horizontal. Season fish on both sides with the fennel, salt and pepper. Lay the vegetables and rosemary over the paper. Season the vegetables with a pinch more of salt and pepper. Lay fish on top of the vegetables. Pour the white wine over everything.
- Seal the packet closed by rolling and crimping the long sides together over the fish and vegetables. Then roll and crimp the ends closed so no steam can escape. Place on a baking sheet.
- Bake for 10-15 minutes, until the fish is cooked through. Just before serving, carefully open the packet (hot steam!) add just a squeeze of lemon juice over everything.