We absolutely love using black lentils for this recipe. But if you can't find them, you could substitute French Green lentils (Lentilles du Puy) instead. French Green lentils also hold their shape well after cooking. But, you'd need to budget budget about 10 to 15 minutes of extra cooking time because they take longer to cook than black lentils. Pro tip: Pay attention to the labels at the store. French Green lentils are dark green—and different than standard "green lentils". Standard green lentils become much softer after cooking, so they aren't recommended as a substitute in this recipe.