1: Start with the pastry. Put the flour and salt into the bowl of a stand with the butter and lard. Using the beater attachment, mix together on a medium speed. When it starts to look like breadcrumbs, change the beater attachment to a dough hook and add 3-4 tablespoons of the cold water. Mix, slowly adding more water to form a dough - you will need to gradually add about another 160-200ml water, just until you get the consistency of a firm bread dough. Once it’s come together, continue to knead the with the dough hook for 4-5 minutes until it’s smooth and quite elastic.
2: Remove from the bowl and wrap in clingfilm, Rest in the fridge for at least 1 hour, or up to a day. While the dough is resting, slice the swede and potatoes into 3mm-5mm slices. I’ve always been told that the potato and swede must be sliced not diced in a pasty so I’m not going to change now! Place the sliced vegetables into a bowl with the onion, cracked black pepper, pinch of salt and chopped flat parsley. Stir in the smoked haddock.
3: Preheat the oven to 180C / Gas Mark 4. Line a baking tray with baking paper.
4: Divide the rested dough into four equal pieces. Shape each piece into a ball. Lightly dust a surface with a little flour and roll each ball out into a rough circle, about 25cm in diameter.
5: Spoon a quarter of the filling into a disc of pastry. Spread the filling onto one half of the disc, leaving the other half clear. Stick a knob of butter on top of the filling. Brush the edges lightly with water then carefully fold the pastry over and join the edges. Push together with your fingers to seal. Crimp the edges together to make sure the filling is held securely inside. You can seal it with a fork or make small twists along the edges and then fold the end corners underneath. Repeat with the rest of the pastry and filling.
6: Put the pasties on the lined baking tray. Brush the top of each one with the beaten egg and sprinkle with a little flaky sea salt. Bake for 40 minutes until golden brown.
7: Cool on the tray for 10 minutes before serving with brown sauce if you like.