Method:

1. First, make your pastry. Place the flour, baking powder, and salt into a food processor and give a quick mix. 450 g (3 2/3 cups) plain (all-purpose) flour, 2 tsp baking powder, 1 tsp salt
2. Add in the butter and whizz until the mixture turns into breadcrumbs. 125 g (1/2 cup + 1 tsp) unsalted butter
3. Add in the egg yolks and mix, then, with the motor on, add in the water a bit at a time until the dough comes together into a ball. You may not need all the water. 2 egg yolks, 125 ml (1/2 cup + 1 tsp) cold water
4. Take the pastry out of the food processor, wrap it in clingfilm or wax paper  and refrigerate for an hour.
5. Preheat your oven to 180C/350F (fan). Take two large baking trays and sprinkle them with some flour.
6. Take your pastry out of the fridge and roll it out on a floured surface until you get a thickness you can cut, that won't tear easily. I find that's about 3mm.
7. Cut circles into the dough using a plate that is about 20-21cm (approx 8") in diameter as a template. I find that I get 3 circles out of the first lot. Then I re-roll and get 2 circles, and then I re-roll and get one final circle. You can place the circles stacked onto a plate so long as you have a sprinkling of flour between each layer.
8. In a large bowl, mix your potato, swede/rutagaba, onion, steak, salt, and pepper. 450 g (1 lb) potato, 150 g (1/3 lb) swede/rutagaba, 150 g (1/3 lb) onion, 300 g (2/3 lb) skirt steak or sirloin steak, 1 tsp salt, 1 tsp ground black pepper
9. Take one of your pastry circles and place it onto your work surface. Place a really good handful of the meat mix onto half of the circle, leaving a 2cm border around the edge. It'll look like a lot of mixture, but it needs to be packed full.
10. Dot 1 1/2 tsp butter (from the 3 tbsp butter) on top of the meat and veg pile. 3 tbsp unsalted butter
11. Take your beaten egg, and using a pastry brush, paint a little of the egg wash around the edge of the circle. This will help the pastry stick together. 1 egg
12. Now, fold the other side of the pastry over the meat until the edges meet and you have a semi-circle. Seal firmly and crimp with your fingers (check out my video above to see how)
13. Place your pasty onto your baking tray and make a little hole in the top using a sharp knife to let out the steam. Repeat with the remaining pasties.
14. Brush the remaining egg wash over the top of the pasties and place in the oven for 50 minutes until golden brown.
15. Take out of the oven and leave to cool for 5 minutes before eating.