Heat the olive oil in a large, heavy-bottomed pot over medium heat. When the oil is shimmering, add the onion, carrots, and celery. Sauté the vegetables for 6-7 minutes, stirring often, or until the vegetables are clear and soft. Add the garlic and tomato paste to the pot. Continue sautéing the ingredients for another minute, till the garlic is fragrant.
Add the lentils, pasta, tomatoes, broth, water, and oregano to the pot. Bring everything to a boil. Reduce the heat to low. Cover and simmer the stew for 15 minutes.
After 15 minutes, add the chopped kale and salt to the pot. Recover and simmer for another 10 minutes. Taste the stew to be sure that the lentils and pasta are both tender; if not, simmer the stew for another 5-10 minutes.
Taste the stew. Add additional salt and freshly ground black pepper to taste, as well as some extra water to loosen the stew up if you like. Divide the stew into bowls and top with cashew Parmesan or fresh chopped parsley leaves, if desired.