Place oil in a large, heavy gauge soup pot. Heat over medium-low heat, then add the onion, carrots, thyme and garlic. Saute for 5-7 minutes until translucent - take care not to burn the garlic! Add salt and pepper and saute for an additional 30 seconds.
Place broth in the pot and bring it to a boil. Once the liquid is bubbling, add the lentils and cooked rice.
Add the carrot tops and stir well. Cook another 5 minutes, stirring occasionally.
Serve hot with fresh grated parmesan (optional)