Heat a generous drizzle of oil in a large saucepan over a medium heat. Add the onions, carrot and celery. Cook for around 10 minutes until the onions are tender.

Dice half of the mushrooms and cut the rest into quarters or thick slices depending on the size of the mushrooms. Add all the mushrooms to the saucepan, along with the garlic and rosemary. Raise the heat a little higher and cook for a few minutes until the mushrooms are glossy and starting to soften.

Add the lentils, stock and tomato paste. Stir well and bring to a boil. Reduce to a simmer and cook for 20 minutes. The lentils should be tender at this stage. Stir through the balsamic vinegar.

Mix the cornflour with a little water to create a slurry. Add to the lentils and stir it through quickly. Cook for another 5 minutes, stirring frequently until slightly thickened.

Remove from the heat. Stir through the cream and parsley. Taste and season generously.

Preheat the oven to 200 degrees Celsius. Spoon the lentils and mushrooms into an ovenproof dish. At this stage there should be plenty of gravy to ensure the filling doesn’t dry out as it bakes.

Brush both sides of each filo sheet lightly with butter. Lightly scrunch each sheet and place it on top of the filling until most of the surface is covered.

Bake for around 30 minutes, until the filo pastry is golden brown and the filling is bubbling.