Whole Salmon Baked in Foil with Tarragon

Ingredients

• 50g butter, melted
• 1 x 1.5kg salmon, cleaned and trimmed
• 1 small bunch tarragon, roughly chopped
• 120ml dry white wine
• Juice of ½ lemon
• Salt and freshly ground black pepper
• 50g shallots, or onion, very finely chopped
• 2 tbsp white wine vinegar
• 4 tbsp dry white wine
• 6 tbsp water or Fish stock
• 2 tbsp double cream
• 175g unsalted butter, cut into small pieces
• Salt and freshly ground white pepper