Great pie, hot out of the oven and served with braised leeks and spinach, but even better the next day cold with pickles and mustard.

Onions 3-4 large

Butter 50g

Good Floury potatoes 400g, peeled, halved and cut into ½ cm slices

Emmental cheese 220g, grated

Mature cheddar or Queijo de Isla 50g, grated

Thick Cream 100ml

PASTRY

Plain flour 150g, plus extra for dusting

Self-raising flour 150g

Sea salt 1 tsp

Butter 150g, chilled and diced

White wine vinegar 1 tbsp

Egg 1, beaten

Method

1. To make the pastry, tip the flours into a food processor and mix with the salt. Tip in the butter and pulse until like breadcrumbs. Whisk the vinegar with 3 tbsp of ice-cold water and the egg and when well mixed drizzle over the flour mix, then pulse again until it starts to clump. Do not be tempted to add more water it takes a minute or two. Wrap in clingfilm and chill in the fridge for 30 minutes or more.
2. Peel the onions  and chop into fairly small pieces. Add to a non-stick pan with 200ml water and the butter. Put on a lid and simmer for 20 minutes, then take off the lid, turn down the heat and cook until most of the moisture has gone and you have very soft onions that are gently frying in the butter but not colouring (this can take 20-30 minutes, so be patient). Take off the heat and cool
3. Put the potatoes into boiling salted water and cook for around 5 – 10 minutes, until soft. They should be really tender but holding their shape. Drain, put back into the hot pan to steam and then cool down (the steaming helps to dry them thoroughly).
4. Lightly flour the worksurface, then rollout ²/3 of the pastry to line a deep 20cm pie tin, keeping the pastry quite thin. Leave an overhang and then put in the fridge while you roll out the other ¹/3 for a lid.
5. Put the onions and potatoes into a bowl and add the cheeses and cream.  Mix gently, taste and add seasoning to taste. Then put gently into the pie dish. Put the pastry lid on top and trim the edges so the bottom and top are the same size, then crimp with your forefinger and thumbs, to seal. Brush the top of the pastry lid with beaten egg, then bake at 190C/fan 170C/gas 5 for 40 minutes until deep golden.

Original recipe at

https://www.olivemagazine.com/recipes/vegetarian/melting-cheese-and-onion-pie/