2 tablespoons vegetable oil
1 large Spanish onion, chopped
4 cloves garlic, crushed
1 stalk celery, chopped
12 ounces roasted, peeled and seeded poblano chiles
2 ounces washed and dried spinach
2 tablespoons kosher salt
1 1/2 teaspoons ground black pepper
8 cups low-sodium chicken broth
3 tablespoons masa harina
Heat oil in large heavy-bottomed saucepan over medium heat; add onion, garlic and celery and cook, stirring, until softened.
Add poblanos, spinach, salt and pepper; cook, stirring, until spinach is wilted. Add stock and bring soup to simmer. Let cook for 15 minutes. Puree with blender.
In small bowl, combine masa harina with enough cold water to make slurry; whisk mixture into soup and return to simmer. Taste and adjust seasonings.
Strain soup through china cap or similar strainer.