Lentil Soup With Winter Vegetables
Ingredients 8 ounces lentils du Puy 1/2 cup (1 stick) unsalted butter 1 cup carrots, finely chopped 1 cup onion, finely chopped 2/3 cup celeriac, finely chopped 2/3 cup leeks, finely chopped 2/3 cup celery, finely chopped 2 sprigs fresh thyme 4 cloves garlic 10 black peppercorns 5 cups homemade or store-bought low-sodium chicken stock, heated, plus more as needed Coarse salt and freshly ground pepper 20 baby spinach leaves...