Take one look and you can see why the optical lens got its name from the lentil. For me, though, the connection between the two runs deeper than their shared form. The lentil has long been one of my favorite foods to cook, because it's one of the best lenses into what I love most about cooking—the transformation of a simple ingredient into something remarkable. This classic French preparation is the one I turn to again and again.
Lentils, by themselves, are not particularly special. They're small, like pebbles, and have an earthy flavor when cooked. Elevating that earthiness isn't hard, but it requires a series of deliberate steps. The goal, mind you, isn't to cover up their natural flavor, but to enhance it—rounding it out, lifting it up, and making it more luxurious.
The first step is when you boil them. Lentils, like all dried legumes, can be tossed into a pot of water and simmered until tender. They can be, but they shouldn't be. Adding aromatics like onion, carrot, celery, and garlic to the bean pot is a critical step that builds in layers of sweet and subtle vegetable flavor. Woodsy herbs like sage, rosemary, and thyme are natural partners to the lentil's earthy flavor, so any of them (or any combination of them) can go into the pot, too. If you've never experienced the superiority of a dried bean over a canned one, it's because you haven't added aromatics and herbs when cooking them.
Next, you want to salt the water generously right from the beginning; you want the water to taste as salty as you like your food to be. Contrary to popular belief, salt not only doesn't prevent the beans from cooking properly, it actually helps them retain their shape better, something we've demonstrated on this site before. Plus, it seasons the beans all the way to the core, something that can't be done when salt is added only at the very end, making every bite more delicious.
Unlike most other beans, lentils don't need to be soaked before cooking, but they do require a watchful eye. Because they're so small, there's a fine line between underdone and mush. I cook them at a very bare simmer, since a more active boil would only jostle them around, breaking them to bits in the process. Once I can smash a lentil against the roof of my mouth with my tongue with no firm resistance, they're done.
The hard part here is that the water they're in is still hot enough to continue cooking them off the heat, and because they're so small, that carryover cooking is enough to overcook them. One option would be to drain the lentils, but I like to keep them in their cooking liquid because that's where all the flavor is. Plus, the skins of lentils and other beans can dry out and grow chapped rapidly once exposed to air. Instead, I drop a handful of ice cubes into the pot to lower the water temperature and stop them from cooking much further.
At this point, the lentils themselves should be surprisingly delicious—well seasoned, and rounded out with the flavors of aromatics and herbs that both soften and deepen the lentils' natural flavor.
The final phase is to finish them, with the goal being to both enrich them with fat, in this case butter, and then balance the butter's richness and the lentils' earthiness with the bright tang of red or white wine vinegar.
I start this part of the process by sweating finely minced aromatics in butter until slightly softened, then I add the drained lentils with just enough of their cooking liquid to form a creamy emulsion with the butter, tossing and stirring to combine it all. I finish it with the wine vinegar until I have a sharp top note to play against all those rich low ones from the beans and butter.
It's not difficult, but it drives right at the heart of what good cooking is all about: building flavors, rounding them out, and brightening them up. All it takes is a watchful eye, and a sharp lens.