In a large soup pot, warm the olive oil over medium heat. Add the onion, carrot, and celery. Stir to coat and cook for 3-5 minutes, stirring occasionally, until the onions are translucent and tender. Add the garlic, stir, and cook for another minute.
Next, add the chopped tomatoes with their juices, season with sea salt and black pepper, and stir to combine. Reduce the heat so the tomatoes gently bubble and cook for 25 minutes, stirring occasionally.
Add the lentils to the pot, stirring to coat. Then, add the broth, another pinch of sea salt, and a few grindings of black pepper. Adjust the heat so the soup cooks at a gentle simmer and cover the pot. Cook for 45 minutes – 1 hour or until the lentils become tender, stirring from time to time so that the lentils don’t stick to the bottom of the pan. Cooking time for lentils varies so makes sure you are tasting and testing. Also, if your soup becomes too thick or dries out at all, simply add more stock to the pot (you can also thin it out with water if you run out of stock).
When the lentils are tender, remove the soup from the heat. Stir in the Parmigiano Reggiano and parsley. Taste and add sea salt and pepper if needed. Finish with a drizzle of extra virgin olive oil.