The mushrooms are bathing in a garlic, thyme and white wine sauce topped with puff pastry, and there’s a layer of spinach just beneath the crust. This is one flavour-packed pie and it looks great when served at the table.
Melt the butter and oil in a large pan over a low-heat.
Add the onion, garlic and thyme with a pinch of salt and pepper.
Sweat for 2-3 minutes until soft, then add the mushrooms.
Turn up the heat and fry for 3-4 minutes until soft.
Add the stock and wine and bring up to the boil briefly, then down to a simmer.
In a bowl, mix the cornflour with a little of the liquor from the pan until smooth and then stir into the pan and continue to heat for 5 minutes until thickened.
When you have a thick gravy, transfer everything to the pie dish and leave to cool completely while you prepare the pastry.
To make the pie
Unroll the puff and, if it’s not wide enough to cover the pie, roll it gently with a rolling pin.
Cut two 2cm (1 inch) wide strips off the shorter edge of the pastry and use them to make a rim around the top of the pie dish.
Pack the fresh spinach on top of the mushrooms, taking care not to leave any stalks sticking up.
Drizzle the spinach with the olive oil.
Put the pastry sheet on top of the pie and press around the rim to seal – I then used the off cuts to add some decorative leaves, held in place with water, but you don’t have to.
Cut two small slits in the centre to allow excess steam to escape, then trim off the edges and brush all over with beaten egg.
Bake for 20-25 minutes until puffed up and a rich, golden brown.