Rinse the lentils in a fine-mesh sieve and discard any stones or debris.

In a deep, heavy pot, warm the vegetable oil over medium-high heat.

Add the chopped onion and carrots and cook, stirring, until the onion is soft, about 5 minutes.

Stir in the rice, curry powder, and lentils; stir until the mixture is fragrant and the beans and rice are coated with oil, about 2 minutes.

Add the 8 cups of chicken broth, cover, and bring to a boil.

Stir again, then decrease the heat to low, and simmer, covered, until the lentils and rice are cooked through, about 30 minutes.

Remove from the heat and let stand for about 10 minutes before serving.

Season well with salt and pepper to taste.

In a small bowl, blend the yogurt and ground cumin.

Ladle the soup into bowls and drizzle a little yogurt on top of each portion.