Heat a large saucepan or medium soup pot on medium heat for one minute. Then add olive oil, the onion, celery and carrot, letting them cook for about 4 minutes. Meanwhile, dice the garlic and prepare the herbs for use. Add garlic, bay leaf and thyme, then season with salt and pepper. Stir once every minute and allow the vegetables to sweat for about ten minutes total. Do not brown the vegetables.
Next add the bacon, lentils, and tomatoes if you are using them. Stir, then add vegetable stock. Let this simmer until the lentils are cooked, about 8 minutes, adding some more water or stock if the liquid level drops too far.
While the lentils are cooking, de-stalk and cut the cabbage leaves and add them to the soup. The water level should cover the cabbage leaves. Cover and simmer for about 5 minutes until the cabbage is cooked, but still nice and green.