Puffed salmon & spinach fish pie - Good Food Middle East

Ingredients

• 1kg Maris Piper potatoes, cut into large chunks
• 2 large eggs, separated
• 400g frozen whole-leaf spinach (frozen weight), defrosted and squeezed dry
• 85g reduced-fat mature cheddar
• whole nutmeg, for grating
• 500g fish - a mix of white and salmon is good (I used 2 frozen salmon fillets and 2 cod, defrosted)
• 1 onion, halved
• a few whole cloves
• 1 fresh or dried bay leaf
• 300ml semi-skimmed milk
• 300ml fish stock (from a cube is fine)
• 25g butter
• 2 tbsp extra-virgin olive oil
• 50g plain flour
• 1 tsp wholegrain mustard