I like this lentil salad best when the diced carrots, onions and fennel are sautéed in olive oil until just-tender, then mixed into the warm lentils along with the vinaigrette. The fennel isn’t necessary (well, neither are shoes) but it’s quite nice if you like it. You can also simmer the vegetables along with the lentils if you want to save a step but be sure to add them to the vinaigrette while warm, which helps them absorb the dressing.
Be sure to use very good olive oil for the vinaigrette: yes, it does make a difference! No cheating. I use Spanish arbequina oil that’s fruity and really quite delicious. Since les lentilles du Puy lend themselves to so many variations, I’ve included a few at then end of the recipe to encourage improvisation.
Serve warm or at room temperature. Cooked lentils will keep in the refrigerator for 2-3 days. They can be reheated in a pan on the stovetop or in a microwave.