Step 1

In a large Dutch oven or heavy pot, cook sausage over medium-high heat until the meat crumbles and begins to brown, about 5 minutes. Add onion, celery and garlic and cook until softened, about 5 minutes.

Step 2

Add stock, lentils, red pepper flakes and tomatoes and bring to a boil. Reduce to a rapid simmer, partially cover, and cook until lentils are tender, 30-35 minutes.

Step 3

Add kale and simmer, uncovered, until tender, 2-3 minutes, Stir in vinegar and season with salt and pepper, to taste. Sprinkle with chopped parsley before serving.