Preheat the oven to 180C/200C Fan/Gas 5.
Roll up the sole fillets and keep in place with a small, sharp wooden skewer.
Grease an ovenproof dish with 1 tablespoon of the butter. Add the sole fillets, oyster juice, half the wine, shallot and fish stock and season with salt and pepper.
Cover tightly with kitchen foil and bake for 10 minutes, turning halfway though, until the flesh is opaque and cooked through.
Spoon 4 tablespoons of the poaching liquor into a saucepan over a medium heat. Add the crème fraîche and double cream and reduce to a thick sauce consistency. Stir in the lemon juice and season with salt and pepper.
In a saucepan over a medium heat, add the remaining 2 tablespoons butter with an equal amount of water. Add the leek and carrot and cook until soft.
In a small saucepan, warm the remaining wine over a low heat and poach the oysters for 3 minutes. Remove the oysters and set aside.
Meanwhile, heat the oil in a frying pan over a high heat. Sear the prawns, flesh-side down, until pink and cooked through.
To serve, divide the sole fillets, prawns and oysters between two plates. Drizzle over the cream sauce and garnish with the vegetables.