Lentil soup is my absolute favorite. I make it several different ways using whatever I have on hand, but this is my favorite:
4 cups vegetable broth
1 cup green lentils, rinsed
1/2 large onion, chopped
1 large carrot, peeled and chopped
2 stalks celery, chopped
1 potato or sweet potato, diced
1 cup canned diced tomatos
2-3 cloves garlic, minced
1 bay leaf
1 tsp. cumin
2 tsp. garam masala (optional)
1 bunch fresh coriander
Drizzle of balsamic vinegar
Salt and pepper
Pour vegetable broth (or water and vegetable bouillion) into large pot. As broth comes to a boil, add lentils, bay leaf and chopped onion, carrot, celery and potato. Add garlic, cumin and garam masala and season with salt and pepper. Stir in diced tomatoes. Reduce heat to low and simmer uncovered until lentils and potatoes are tender, approximately 1 hour. Remove bay leaf, mix in a drizzle of balsamic vinegar and adjust salt, pepper and vinegar to taste.
I like to transfer about 2 cups of the finished soup to the bowl of a food processor, puree and mix back in with remaining soup for an interesting texture.
If at any point the soup is too thick for your taste, simply add water. This is particularly useful when reheating leftovers.