Preheat the oven to 350°F (180°C).

Thinly slice the onion, leek, and mushrooms. Sauté them in a hot skillet with a drizzle of olive oil. Add the bacon pieces and season with pepper.

Roll out the pie crust in a tart pan and prick the bottom with a fork.

In a bowl, beat the eggs with the cream. Season with salt and pepper.

Spread the leek, bacon, and mushroom mixture in the tart pan, then pour the egg and cream mixture over it.