1. Wash, dry, and slice the mushrooms and leek, then cut the ham into cubes.
2. Preheat your oven to 180°C (350°F).
3. In a buttered pan, sauté the mushrooms and leek until all the cooking liquid has evaporated. Season with salt and pepper.
4. Meanwhile, beat the eggs with the cream, grated cheese, and ham cubes.
5. Roll out the pastry in a buttered tart pan, then fill the bottom with the leek and mushroom mixture.
6. Pour the egg and ham mixture over the top, and bake in a hot oven for 1 hour.