Fish pie

Ingredients

• 900g Floury Potatoes
• 2 tbsp Olive Oil
• 600ml Semi-skimmed Milk
• 800g White Fish Fillets
• 1 tbsp Plain flour
• Grating Nutmeg
• 3 tbsp Double Cream
• 200g Jerusalem Artichokes
• 1 finely sliced Leek
• 200g peeled raw Prawns
• Large handful Parsley
• Handful Dill
• Grated zest of 1 Lemon
• 25g grated Gruyère
• Juice of 1 Lemon