Turn the heat to high under a large deep skillet and add the lamb a little at a time, breaking it into small pieces as you do. Stir and break up the meat a bit more, then add the cooked lentils. Keep the high heat and continue to cook, stirring occasionally, until the lentils begin to brown and pop, 5 to 10 minutes. Don't worry if the mixture sticks a bit, but if it begins to scorch, lower the heat slightly.
Add the cumin, chile, and garlic and cook, stirring, for about a minute. Add the reserved lentil liquid and stir, scraping the bottom of the pan to loosen any browned bits. Season with salt and pepper, turn the heat to medium-low, and cook until the mixture is no longer soupy but not dry.
Stir in the olive oil, then taste and adjust the seasoning. Garnish with cilantro if you like, and serve immediately, with yogurt and rice or pita bread.
Before starting Food52 with Merrill, I was a food writer and editor at the New York Times. I've written several books, including "Cooking for Mr. Latte" and "The Essential New York Times Cookbook." I played myself in "Julie & Julia" -- hope you didn't blink, or you may have missed the scene! I live in Brooklyn with my husband, Tad, and twins, Walker and Addison.