Place sausage in the bottom of a 4-quart pot and cook on medium-high heat, breaking it up with a wooden spoon or fork as it cooks. Meanwhile, chop onion and carrot and add to the sausage to cook. (If the sausage gives up a lot of fat, you may want to drain some of it before you add the vegetables. I haven't had this problem with Italian bulk sausage.)
When the onions are translucent, add the lentils, broth and enough water to make 2 quarts (8 cups) of liquid. Bring to a boil and cook 30 minutes.
Meanwhile, wash Kale and trim off woody stems. Slice leaves about one-half-inch thick. After soup has cooked 30 minutes, add kale and cook until lentils are tender and kale is cooked as you like it (about 20 minutes).
Add salt and pepper to taste (this soup is also good with a hot pepper added when you cook the onion and carrot).
Dish out into individual bowls, sprinkle with feta cheese and serve with hot rolls, rye toast (or, if you have time to make it, corn bread). Makes 4 servings.