Fabulous Freezer Fish Pie- Justine Pattison's fabulous and easy recipe

Ingredients

• 500 g thick white fish fillets, (such as cod or haddock)
• 300 g smoked haddock fillet
• 300 g thick salmon fillet
• 750 ml full fat or semi-skimmed milk
• 1 medium onion, (cut into wedges)
• 2 bay leaves
• 75 g butter
• 75 g plain flour
• small bunch of fresh dill (roughly 15g or 2 tsp freeze-dried dill
• flaked sea salt
• freshly ground black pepper
• Cheesy potato topping
• 1.25 kg medium potatoes, (preferably Maris Piper)
• 300 ml tub half-fat crème fraiche
• 50 g mature Cheddar cheese, (finely grated)