Rinse the lentils in a colander and pick out any stones. Combine them in a pot with 4 cups stock and bring to a boil. Reduce the heat and simmer until the lentils are tender, about 20 minutes. Meanwhile, heat the oil or ghee in a medium skillet and sauté the onion over medium heat, stirring frequently, until browned in spots but not burnt, about 10 minutes or so. Add the garlic and spices and fry until aromatic, about 30 seconds. Scrape into the lentils and add coconut milk, kale, and mushrooms. If soup is too thick, add up to 2 more cups stock. Bring soup back up to a boil then reduce heat to a simmer and let cook for about 10 minutes, or until mushrooms are cooked and kale is tender. Add salt to taste.