Place a large soup pot over medium-high heat with one turn of the pan of EVOO, about 1 tablespoon. Once hot, add the sausage and saut for 3-4 minutes, breaking it up into small pieces with the back of a spoon or a potato masher as it cooks and browns.
While the sausage is browning, pour the lentils out onto a light-colored plate and sift through them. Discard any small stones -- sometimes you find them sometimes you don't, but better safe than sorry.
To the browned sausage, add the onion, garlic, mushrooms, potato, rosemary, thyme, salt, pepper and the tomato paste. Cook, stirring frequently, for 3-4 minutes.
Add the stock and 2 cups of water, turn the heat up to high and bring up to a bubble. Add the lentils and the kale, stir until the kale wilts in then turn the heat down to medium and simmer 30-40 minutes, until the lentils are tender. Serve.