Rinse lentils in a fine mesh strainer and drain.

Brown sausage in a skillet drizzled with olive or canola oil. Remove sausage to a **paper towel to drain, but leave drippings in the pan.

Saute lentils in the sausage drippings for a couple of minutes. Remove them to a 6-quart saucepan.

Combine lentils with 6 cups of stock and add bay leaf. Bring to a boil for 5 minutes. Cover and allow reduce to a simmer for 40 minutes.

While lentils cook, In the skillet that sausage cooked in, add 1 or 2 teaspoons of olive or canola oil if no drippings remain. Add Carrots, celery, and onion. Salt and pepper. Saute until they begin to soften.

In a small pan, roast fennel, cumin, and coriander seed until fragrant. Grind in a spice or coffee grinder.

Add spices, crushed red pepper, if using, and garlic to sauteed vegetables. Cook for another minute.

Using an immersion blender, blend lentils lightly. You still want whole lentils visible. Blending thickens the soup.

Combine sausage and vegetables with lentils. Cover with additional stock to get the desired thickness. Salt and pepper to taste. Heat through. Remove bay leaf.

Serve with chopped cilantro and a dollop of yogurt and other garnishes as desired.