Mix all the ingredients together in a stand mixer or food processor and mix just until the dough forms a ball. Wrap in cling film and leave to rest in the fridge for 30 mins. Remove the dough from the fridge and leave to stand about 10 minutes, to make it easy to roll it out.

Roll out the pastry on a lightly floured surface. Then, roll the pastry around the rolling pin to transfer it to a 28cm/11 inch tart tin.

Press the pastry well into the sides. Roll over the top of the tin to clean up any rough edges. Chill in the fridge for 30 minutes (this is important so the sides won’t fall during baking later).

Preheat the oven to 200°C/180°C fan (400°F/Gas 6).

If making a large tart, blind bake for 15 minutes covered in parchment and baking beans or rice. No need for tartlets.

If using a hard pumpkin like potimarron/Red Kuri squash, roast whole in the oven for 15 minutes. This will make it easier to cut into small chunks (no need to cut off the skin, it’s edible). Let cool slightly to spoon out the seeds.

Place the chopped pumpkin with 2 tablespoon of the olive oil and chopped sage in a roasting tin. Roast in the oven for 20 minutes.

No need to do this if using purée – see NOTES.

Meanwhile, over medium heat, dry fry the mushrooms: there’s no need to add any oil. Wait until the mushrooms give off their liquid then transfer to a plate. Set aside to cool slightly.

In the same pan, add the remaining olive oil and gently fry the sliced leek until translucent but not brown.

In a bowl, whisk together the eggs, crème fraîche, nutmeg, grated cheese and season to taste.

Sprinkle the roasted pumpkin and sage over the tart base, top with the leek and mushrooms and pour over the creamy egg mix. Bake in the oven for about 30 minutes.