Nona's Umbrian Lentil Soup

This crockpot recipe comes from Slow Cooker: The Best Cookbook Ever. Add more salt and pepper.

3T extra virgin olive oil
1 large onion, coarsely chopped
2 cloves garlic, left whole
3 medium carrots, coarsely chopped
6 stalks of celery, coarsely chopped
2 T fresh sage leaves
1 28 oz can of whole tomatoes, undrained
2 C green lentils
6 C chicken broth
salt and pepper
Heat oil in a large skillet over medium heat. Saute the onion, garlic, celery, carrots and sage about 3-4 minutes. Add the tomatoes and cook for 2-3 minutes. Transfer all to a slow cooker. Add lentils and broth to the crockpot. Cook on low for 8 hours. Check after 3 hours if there is enough liquid. Serve with grated cheese.