Fifty minutes, four people, a single baked dish: that's all this leek recipe asks of you, and it's one of the easiest to get right on a weeknight.
Leeks often get a bad reputation, relegated to Sunday night soup. Yet a leek-based recipe, nicely browned in the oven, can become a main course or a side dish the whole table enjoys. And among baked leek recipes, the béchamel version remains the most reliable one to start with.
Baked leeks au gratin with béchamel take 50 minutes to make and serve 4.
To get this leek recipe right, three rules matter. Drain the cooked leeks well before covering them with sauce, otherwise the béchamel turns runny. Don't let the flour brown in the butter. And bake in a hot oven for a golden crust, not a soggy gratin.
Ingredients
- 8 medium leeks (about 1 kg)
- 40 g butter
- 30 g flour
- 50 cl whole milk
- 100 g grated Comté or Gruyère
- 1 pinch of nutmeg
- Salt, freshly ground pepper
Step-by-step recipe
- Prepare the leeks. Trim off the roots and the dark green tops, split each leek in half lengthwise and rinse under cold water to remove the soil between the leaves.
- Boil the leeks. In a large pot of salted boiling water, cook the leeks for 12 to 15 minutes, until tender when pierced with the tip of a knife.
- Drain thoroughly. Lift out the leeks, drain them and gently squeeze them between your hands or in a dish towel to remove excess water before arranging them in the dish.
- Preheat the oven. Set the oven to 200°C, which is thermostat 6 to 7.
- Make the béchamel. Melt the butter in a saucepan over low heat, add the flour all at once and stir for one minute without letting it brown. Off the heat, pour in the milk little by little, whisking to prevent lumps, then return to medium heat and let it thicken for 5 minutes, stirring constantly. Season with salt and pepper, and add the nutmeg.
- Assemble the gratin. Arrange the drained leeks in a buttered baking dish and cover them with the hot béchamel.
- Sprinkle with cheese. Cover the top with grated Comté or Gruyère.
- Bake. Bake for 20 minutes, until the top is golden and bubbling, then let rest for 5 minutes before serving.
The chef's tip
The secret to a successful leek gratin is water. Boiled leeks always hold on to some of it, and if you put them in the dish wet, the béchamel thins out and the gratin ends up runny. Really squeeze them, in a clean dish towel if needed, until no more water comes out. Another useful trick: if the top isn't golden enough after 20 minutes at 200°C, slide the dish under the oven broiler for two minutes, watching it closely. It browns the top without drying out the béchamel underneath.
With what you have
- Leeks with ham: wrap a slice of cooked ham around each leek before covering with béchamel, for a complete meal.
- With potatoes: add sliced steamed potatoes to the bottom of the dish for a heartier leek recipe.
- Lighter version: replace the béchamel with light crème fraîche mixed with a spoonful of mustard, no cooked sauce needed.
- With a stronger cheese: replace the Comté with crumbled Roquefort for a bolder version, perfect alongside red meat.
Frequently asked questions
Can I make this recipe with frozen leeks?
Yes, as long as you drain them well. Frozen leeks are already blanched: simply thaw them, squeeze out the excess water and warm them for a few minutes in a pan before arranging them in the dish. The result is a little less firm than with fresh leeks, but the gratin still turns out well.
How do I know if the leeks are cooked enough?
Pierce the base of the leek with the tip of a knife. If it slides in without resistance, they're done. An undercooked leek stays stringy to the bite, even covered in béchamel and baked, so if in doubt, it's better to boil them a few minutes longer.
Can I make this leek gratin ahead of time?
Yes. Prepare the dish up to the grated cheese step, cover and keep it in the refrigerator for up to 24 hours. Take it out fifteen minutes before baking so it doesn't go into the oven too cold, and allow five extra minutes of baking time.
Cooking with the right apron
Before landing in this gratin, leeks have often come from a vegetable garden. If you grow your own vegetables, a sturdy gardening apron protects your clothes in the soil as well as in the kitchen. And for what comes next, béchamel and melted cheese included, a well-cut kitchen apron does the job too.
Le Tablier du Chef, kitchen and workwear aprons, online.
