Warm Lentils with Braised Leeks and Mustard Vinaigrette
Leeks braised in olive oil until silky, folded through warm green lentils with diced carrot and thyme, dressed while everything is still hot with a sharp Dijon and cider vinaigrette and finished with watercress.
Why You'll Love This Recipe
I learned this the way most people do, by eating leeks vinaigrette in a French cafe and wondering why something so plain was so good. The answer is that leeks cooked slowly in fat stop being a soup vegetable and turn into something closer to a custard, sweet and slippery, and that a sharp mustard dressing is the only sensible thing to put against them. Adding lentils turns a first course into lunch. I cook the leeks cut side down and leave them alone long enough to take real color, because that browned face is where most of the flavor comes from.
The trick that makes this dish, and it is not much of a trick, is dressing everything while it is hot. Warm lentils drink vinaigrette. Cold ones sit in it. So the mustard, vinegar, and shallot go into the bowl first, the hot lentils go straight on top, and by the time you have arranged the leeks the dressing has disappeared into the beans and the whole thing tastes seasoned all the way through rather than only on the surface. The watercress is the last thing and the only cold thing, and it is there for the pepper and the crunch.
This belongs on a weekday, made ahead, and it is one of the few lunches that is genuinely better on day two than on day one. It travels perfectly, it does not need reheating, and it is the sort of plate that makes the middle of the day feel deliberate rather than accidental. In winter I add a spoonful more mustard and eat it warm out of the pan. In summer I let it come to room temperature and pile on twice the watercress.
Ingredients
- 3 tbsp extra virgin olive oil, divided
- 3 large leeks (about 1 lb trimmed), white and pale green parts, halved lengthwise and rinsed well
- 2 medium carrots, cut into 1/4-inch dice
- 1 large shallot, finely minced
- 2 garlic cloves, finely minced
- 1 tsp fresh thyme leaves
- 1 dried bay leaf
- 2 cups cooked French green lentils (about 14 oz), drained
- 1 tbsp Dijon mustard
- 1 1/2 tbsp cider vinegar
- 1/3 cup chopped flat-leaf parsley
- 2 loosely packed cups watercress, thick stems pinched off
- 1/2 tsp coarsely ground black pepper
- a scant 1/4 tsp fine sea salt
Instructions
- Clean and halve the leeks: Trim the roots and cut away the dark green tops. Halve each leek lengthwise and fan the layers open under cold running water until it runs clear at the base, since grit hides several layers in. Cut each half into 3-inch lengths and pat them dry on a towel, because a wet leek steams rather than browns.
- Brown the leeks cut side down: Heat 2 tbsp of the olive oil in a large skillet over medium heat. Lay the leek pieces cut side down in a single layer, season with half the salt, and leave them completely alone for five to six minutes. Lift one to check: you want a deep golden face, not pale and not scorched. Turn them over.
- Braise them soft: Add the carrot dice, the thyme, the bay leaf, and 1/2 cup of water to the pan. Cover, drop the heat to low, and cook for twelve to fourteen minutes, until a knife slides through the thickest part of a leek with no resistance at all. Uncover, add the garlic, and cook one more minute so any remaining water evaporates and the pan goes glossy again.
- Make the vinaigrette in the serving bowl: While the leeks braise, whisk the Dijon, the cider vinegar, the minced shallot, the black pepper, and the rest of the salt in a wide serving bowl. Stream in the last tablespoon of olive oil while whisking. It should be thick enough to coat the back of a spoon and taste distinctly sharp on its own, since the lentils will soften it considerably.
- Dress everything hot: Warm the lentils through, in a saucepan with a splash of water or in the microwave, and tip them into the bowl with the vinaigrette while they are steaming. Fold gently so they take on the dressing without breaking. Fish out the bay leaf, then lay the leeks and carrots over the top with any pan juices. Scatter the parsley, pile the watercress on at the very end, and serve warm or at room temperature.
Variations
- With a soft-boiled egg: Halve a six-and-a-half-minute egg over each plate and let the yolk run into the mustard dressing.
- Roasted rather than braised: Toss the leek pieces in oil and roast at 425°F for twenty five minutes for a drier, more caramelized version with crisp edges.
- Add fennel: Braise a thinly sliced fennel bulb alongside the leeks for an anise note that suits the mustard well.
- Tarragon in place of thyme: Fold a tablespoon of chopped fresh tarragon into the vinaigrette for a distinctly French, faintly sweet turn.
- Walnuts on top: Scatter a handful of toasted walnuts over the finished plate for crunch against the soft lentils.
Storage & Leftovers
Kept sealed in the refrigerator this is good for four days, and the lentils go on absorbing the mustard and vinegar the whole time, which is why day two tastes more complete than day one. Store the watercress separately in a bag with a dry paper towel so it stays crisp, and add it as you serve.
There is no need to reheat it. This is a dish that is meant to be eaten at room temperature as often as warm, so take it out of the refrigerator twenty minutes before you want to eat, which is enough to bring the olive oil back from cloudy to clear. If you do want it hot, a covered pan over low heat for four minutes with a spoonful of water is gentler than a microwave on the leeks.
Do not freeze the finished dish. Braised leeks turn to threads and the vinaigrette separates. Cooked lentils, on the other hand, freeze beautifully on their own in one-cup portions for up to three months, so cooking a large pot and freezing it is what makes this a fifteen-minute lunch on a weeknight.
Notes & Tips
- Dry the leeks before they hit the pan: Washed leeks hold water between their layers. Five seconds with a towel is the difference between a golden cut face and a pale steamed one.
- Leave them alone once they are down: Moving the leeks around in the first five minutes stops them coloring. Set them cut side down, walk away, and trust the pan.
- Dress the lentils while they steam: This is the single step that decides whether the dish tastes seasoned through or only on top. Warm beans absorb vinaigrette; cold beans wear it.
- Mince the shallot fine and let it sit in the vinegar: Even five minutes in the acid takes the harsh edge off and turns it sweet, so make the dressing before you start the leeks.
- Cook lentils in unsalted water: Salt early in the pot firms the skins and they take much longer to soften. Season them once they are drained and still hot.
- Keep the watercress for the plate: Folded in early it wilts to nothing. Piled on at the table it stays cold and peppery against the warm lentils, which is the contrast the dish is built on.
Nutrition & Mindful Eating
- Lentils, leeks, and a mustard vinaigrette are doing three separate jobs here. The lentils give the plate its substance, the leeks give it the sweetness and the silky texture, and the sharp dressing keeps a bowl of legumes from ever tasting heavy or plain.
- French green lentils hold their shape rather than collapsing, so you taste each one, and they bring both protein and a good amount of fiber to a plate that has no meat on it at all.
- Leeks are alliums, gentler and sweeter than onions, and slow cooking turns their fibers into something close to velvet. That fiber is the kind that feeds the bacteria in your gut, and it is also why they take longer under the lid than you expect.
- Watercress goes on cold and stays peppery, and this is one of those small dark leaves that carries far more calcium and vitamin K than something so delicate looks like it should.
- Dijon, cider vinegar, and minced shallot are the whole seasoning, and the acid is what makes the dish work. It cuts through the olive oil, lifts the sweetness of the leeks, and gives every forkful a clean edge.
- As you eat, notice how completely the leeks have given way against the firm little lentils, and let the cold watercress on top slow you down between forkfuls.
Frequently Asked Questions
How do I cook the lentils from dried?
Use about 1 1/4 cups dried French green lentils, which are the small dark ones that hold their shape. Cover them with three inches of unsalted water, add a bay leaf and a halved shallot, and simmer for twenty to twenty five minutes until they are tender with no chalk in the middle. Drain, discard the aromatics, and use them warm.
Can I use brown or red lentils?
Brown lentils work if you watch them closely, since they go from firm to blown out in about three minutes. Red lentils will not work here at all, because they collapse into puree by design. If green lentils are hard to find, small brown ones cooked two minutes short of tender are the best substitute.
My leeks are still squeaky in the middle. What happened?
They needed longer under the lid. Leeks are stubborn, and thick winter ones can take twenty minutes rather than twelve. Test the fattest piece with the tip of a knife and keep going with another splash of water until it meets no resistance, because slightly overcooked leeks are lovely and undercooked ones are not.
Is the mustard supposed to be this assertive?
In the bowl on its own, yes. A vinaigrette tasted by itself should be sharper than you would want to eat, because a pound of lentils and leeks will round it right off. If it tastes balanced before it meets the food, the finished plate will taste flat.