Toast the coriander and caraway till fragrant. Finely grind the coriander and caraway.
Add some oil to a 5qt saucepan. Heat to medium and add onions and carrot. Saute till soft, around 10 minutes.
Add the coriander, caraway, and garlic to the onions. Cook for about 2 minutes.
Add stock and lentils. Bring stock to a boil. Cover, and simmer for about 20 minutes or until lentils are done.
Puree the soup and adjust seasonings.
Mix the yogurt and 3/4 of the mint.
Serve the soup with a dollop of the yogurt in the center and sprinkle with some more mint.
Coarsely chop the carrots and onions