Preheat the oven to 180C/350F/Gas 4.
Using a sharp knife, score the skin of the trout diagonally at 2cm/½in intervals.
Cut a sheet of foil about 30cm/12in square and lay a square of baking parchment of the same size on top. Place the pile of spinach in the centre of the baking parchment, followed by the trout fillet, the lemon slices, dill and white wine. Season with salt and freshly ground black pepper.
Bring the sides of the foil together over the fish and secure. Scrunch the two open ends together to make a 'tent' for the fish. Place on a baking tray and cook for 8-10 minutes, or until cooked through.
To serve, place the foil parcel onto a serving plate and open it up.