Preheat your oven to 190°C (375°F). Roll out the chilled pie crust on a floured surface to about 3mm thick. Carefully transfer it into your tart pan, trimming the excess dough. Chill the crust for 10 minutes to relax the gluten.
Line the chilled crust with parchment paper, then fill with pie weights or dried beans. Bake the crust for about 15 minutes until the edges are just golden. Remove from the oven and set aside.
While the crust bakes, prepare the leeks. In a large skillet over medium-low heat, melt the butter. Add the sliced leeks along with a pinch of salt. Cook slowly, stirring occasionally, until they turn a deep golden brown and become fragrant—about 20-25 minutes. They should be soft and caramelized, with a smoky sweetness.
In a mixing bowl, whisk together the eggs, heavy cream, nutmeg, salt, and pepper until smooth and slightly frothy. Stir in the grated cheese.
Spread the caramelized leeks evenly over the baked crust. Pour the custard mixture over the leeks, ensuring an even layer. Gently tap the tart to settle the filling.
Place the tart on a baking sheet and bake for 35-40 minutes, until the top is golden brown and the custard is just set with a slight wobble in the center. Cover the edges with foil if they brown too quickly.
Remove the quiche from the oven and let it rest for 10 minutes. This allows the filling to set further and makes slicing easier. The top should be fragrant and beautifully golden.
Slice the quiche into wedges and serve warm or at room temperature. Enjoy the tender, smoky leeks combined with cheesy, creamy filling and flaky crust for a comforting, elegant meal.
