Humble Pie, a Mary Berry recipe, it’s vegetarian and cheesy

1 large cauliflower
2 leeks, trimmed and cut into 2cm/¾in slices
knob of butter
200g/7oz button mushrooms, halved
115g/4oz frozen petits pois peas
salt and freshly ground black pepper
For the cheese sauce

55g/2oz butter
55g/2oz plain flour
450ml/¾ pint hot milk
2 tsp Dijon mustard
115g/4oz mature cheddar, coarsely grated
55g/2oz Parmesan, coarsely grated (or alternative vegetarian hard cheese)
salt and freshly ground black pepper
To assemble

375g ready-rolled puff pastry

1 free-range egg, beaten

For those who like or prefer low carb/keto,

Method
1. Preheat the oven to 200C/180C Fan/Gas 6.
2. Break the cauliflower into fairly small, even-sized florets. Some of the smaller leaves can be chopped into pieces.
3. To make the vegetable filling, bring a large pan of salted water to the boil. Add the leeks and boil for 4 minutes. Add the cauliflower florets and leaves, and bring back to the boil for 3 minutes until just tender. Drain and run under cold water to stop the cooking. Drain well and set aside.
4. To make the cheese sauce, melt the butter in a large saucepan over a medium heat. Sprinkle in the flour and stir for 1 minute. Gradually add the hot milk, whisking until thickened. Stir in the mustard, cheddar and Parmesan, then season well with salt and freshly ground black pepper. Leave to cool for 5 minutes.
5. To finish the vegetable filling, heat the knob of butter over a high heat. Add the mushrooms and pan-fry for 3 minutes until golden. Season with salt and pepper, then set aside to cool. Add all the cold vegetables and frozen peas to the cheese sauce, stir and check the seasoning. Spoon into the pie dish.
6. Unroll the pastry and cut a 7cm/2¾in strip from the short side and chill this in the fridge. Roll out the remaining pastry to slightly bigger than the top of your pie dish. Brush beaten egg around the edge of the dish, then place the pastry on top and press down on the edges to seal. Trim any excess pastry with a sharp knife and make a small slit in the centre for the steam to escape. Brush the top with beaten egg.
7. Roll out the reserved strip of pastry to be a bit thinner, then roll it up tightly. Using a sharp knife, slice to make long thin strips. Unravel and dip them into the egg wash, then arrange on top of the pie, in a random pattern. Bake for about 40–45 minutes, until the pastry is golden and the sauce is bubbling around the edges.

Recipe Tips
i) The pie can be made, left unglazed and kept covered in the fridge for up to 24 hours ahead.
ii) Not suitable for freezing.