-
1
Heat the olive oil over medium heat in a large, heavy soup pot or Dutch oven, and add the onion and celery.
-
2
Cook, stirring, until tender, about 5 minutes.
-
3
Add a generous pinch of salt and the garlic and cook, stirring, until the garlic smells fragrant, 30 seconds to 1 minute.
-
4
Add the stock, rice, bouquet garni, and salt to taste, and bring to a boil.
-
5
Reduce the heat, cover and simmer 30 minutes.
-
6
Remove the bouquet garni.
-
7
Stir in the spinach and spices, cover and simmer 5 minutes, stirring once or twice.
-
8
The spinach should wilt but should maintain its bright color.
-
9
Using a hand blender that has a powerful motor, or in batches in a regular blender, puree the soup.
-
10
If using a regular blender, fill only halfway and cover the top with a towel pulled down tight, rather than the lid, because hot soup will push the top off if the blender is closed airtight.
-
11
Return to the pot and heat through, stirring.
-
12
Whisk 1 teaspoon cornstarch into 1 cup of the yogurt, and whisk into the soup.
-
13
Season to taste with salt and pepper.
-
14
If you want a pungent, garlicky yogurt garnish, mash the remaining garlic to a paste with a pinch of salt in a mortar and pestle.
-
15
Stir into the remaining yogurt.
-
16
Serve the soup, garnishing each bowl with a swirl of the yogurt and a sprinkling of chopped walnuts.
