Lentil Soup with butter

1 cup red lentil 2 tablespoons virgin olive oil 1 onion , finely chopped 1 -2 carrot , finely chopped 1 -2 celery rib , finely chipped 3 garlic cloves ,[...]

1 lb potato , peeled and cut into small cubes 10 ounces green lentils (not Puy) 6 garlic cloves , unskinned 1 large carrot , scraped and chopped 2 celery ribs[...]