Heat the olive oil in a large heavy bottomed pot over medium low heat. Saute the leeks and garlic. Season with salt. Cook until translucent. Add the carrots, potatoes and green beans, cooking for another 4-5 min.
Pour in the stock and bring to a boil. Then add the tomatoes, corn, Thyme and season again with salt and pepper. Reduce heat to simmer and cook for 20 min. Add in lentils and cook for 18-20 min. don't let them go to a mush. Add the lemon juice before serving and adjust seasoning if necessary. Garnish with parsley.
Nutrition calculation is an estimation only. If you need nutritional calculations for medical reasons, please use a source that you trust.