500g pack bread mix
2 tsp mustard powder
500g bag new potatoes
500ml tub crème fraîche
175g/6oz extra-mature cheddar, grated, plus a little extra to scatter on
small bunch parsley, chopped
a little plain flour, for dusting
1 bunch spring onions, sliced
400g/14oz thick sliced lean ham, diced, any fat removed
1 tbsp olive oil, for greasing
1 egg, beaten
Tip the bread mix into a large bowl and stir in the mustard powder, then make up following pack instructions. Cover with oiled cling film and leave to rise in a warm spot for 45 mins-1 hr until doubled in size.
Meanwhile, bring a large pan of salted water to the boil, add potatoes and cook for 10-12 mins until tender. Drain, leave in a colander until cool enough to handle, then peel off skins and chunkily dice.
Mix the crème fraîche, cheddar and parsley, then season really well.
Roll out just under half the dough on a floured surface to a 25cm circle – it’s easier to use a rolling pin and stretch it with your hands at the same time. Lift onto a floured baking sheet that will fit into the freezer. Evenly pile the potatoes on top, leaving a good 2-3cm border. Dot half the crème fraîche mixture on. Follow with the spring onions, then the ham, then dot remaining crème fraîche mixture all over the top. Roll out remaining dough as you did the first, to a little bit bigger than 25cm. Brush the border of the bottom of the pie with water, then lift the top onto the pie. Trim if you need, then press and roll up the border edge to seal. Do this all the way around, then press with the prongs of a fork to really seal it well. The pie is now ready to freeze, brush some cling film with a little oil and wrap it up well. Freeze for up to 2 months.
Bring the pie out of the freezer in the morning and leave at room temperature for about 3 hrs.
Heat oven to 160C/140C fan/gas 3. Brush the frozen pie with beaten egg, scatter with a little more cheese if you like, and cover with foil. Bake for 1 hr, then remove the foil and bake for 1 hr more until golden and crisp – poke a skewer into the middle and check it’s piping hot all the way through.