Cheesy Leek and Potato Fish Pie

1. Prepare the Pastry:

• In a food processor, combine 400g plain flour, 1 tsp fine salt, ½ small bunch of thyme (leaves picked), and ½ tbsp English mustard powder. Pulse briefly to mix.
• Add 180g cold unsalted butter (cut into cubes) and pulse until the mixture resembles fine breadcrumbs.
• Pour in half of the beaten egg and 1 tbsp cold water, pulsing until the dough starts to come together. If it’s too dry, add 1-2 more tbsp cold water as needed.
• Transfer the dough to a lightly floured work surface and knead it briefly. Wrap in cling film and chill in the refrigerator for 30 minutes.

2. Make the Filling:

• While the dough chills, peel and chop 1 potato (about 270g) into 3cm chunks. Place in a pan of boiling water and cook for 8-10 minutes until tender. Drain and let steam dry.
• In a large frying pan, heat 1 tbsp olive oil and 50g butter over medium heat. Add 2 leeks (finely sliced) and sauté for 5 minutes until soft.
• Stir in 3 tbsp plain flour and cook for 2 minutes. Gradually add 400ml whole milk, stirring continuously to avoid lumps.
• Once combined, add 100ml double cream, 100g mature cheddar (grated), and 3 tsp Dijon mustard. Stir and cook for 1-2 minutes until the cheese melts.
• Fold in the ¼ bunch of chives (finely chopped), season with salt and pepper, and remove from heat. Let it cool for 15 minutes.

3. Assemble the Pie:

• Preheat your oven to 220C/200C fan/gas 8.
• Gently fold in the 200g skinless salmon fillet (cut into chunks), 200g skinless smoked haddock fillet (cut into chunks), and 100g raw king prawns (peeled) into the cooled leek mixture.
• Spoon the filling into a 27cm round pie dish.
• On a lightly floured surface, roll out the chilled pastry to about the thickness of a £1 coin.
• Drape the rolled pastry over the pie filling, trimming any excess dough. Crimp the edges to seal.
• Use any pastry scraps to decorate the top if desired. Brush the pastry with the remaining beaten egg.

4. Bake:

• Place the pie in the center of the oven and bake for 35-40 minutes until the pastry is golden brown.

5. Serve:

• Let the pie cool slightly, then serve warm with steamed greens on the side. Enjoy!