Spinach bouillabaisse [Photo/The New York Times]

The license to call this nourishing one-dish meal a bouillabaisse comes with the generous pinch of saffron that is added to the broth. It is one of many humble, filling and comforting vegetable soups from Provence that are given that lofty title.

2 pounds spinach, stemmed and washed in 2 changes of water, or 1 pound baby spinach, rinsed

2 tablespoons extra virgin olive oil

1 onion, finely chopped

2 leeks, white and light green parts only, cut in half lengthwise and rinsed of all grit, then sliced thin

Salt to taste

6 garlic cloves, minced

1 pound Yukon gold potatoes

A bouquet garni made with a bay leaf and a couple of sprigs each thyme and parsley (and if you have it, a fennel sprig)

Generous pinch of saffron

Freshly ground pepper

6 eggs

1 1/2 ounces Gruyre cheese, grated (6 tablespoons)

12 thin slices baguette, toasted (optional)

1. Bring a large pot of water to a boil while you prepare the spinach. When the water comes to a boil, salt generously and add the spinach. Blanch for 30 seconds and transfer to a bowl of cold water without draining the water from the pot. Measure out 2 quarts of the boiling water and set aside. Drain the spinach, squeeze out excess water and chop coarsely. Set aside.

2. Heat the olive oil in a large, heavy soup pot or Dutch oven and add the onion and leek. Cook, stirring often, until tender, about 5 minutes. Add a generous pinch of salt and the garlic, stir over medium heat until the garlic smells fragrant, no more than a minute, and stir in the broth from the spinach, the potatoes, bouquet garni and salt to taste. Bring to a boil, add the saffron, and turn the heat to low. Cover and simmer 20 to 30 minutes, until the potatoes are tender but still intact and the broth is fragrant.

3. Stir in the spinach, cover and continue to simmer for another 10 minutes. Add pepper, remove the bouquet garni, taste and adjust seasonings.

4. Keep the soup at a bare simmer. Break each egg into the soup (I prefer to first break the egg into a teacup and then tip it into the soup). Cover and continue to simmer until the eggs are set, about 5 minutes.

5. Serve the soup in wide bowls with an egg in each one. Sprinkle gruyere over each egg, and garnish if desired with toasted rounds of baguette or whole-wheat bread rubbed with garlic.

Yield: 6 servings.

Advance preparation: You can prepare the soup through Step 2 several hours ahead, or even a day ahead (refrigerate overnight).

Nutritional information per serving(6 servings): 255 calories; 12 grams fat; 4 grams saturated fat; 2 grams polyunsaturated fat; 6 grams monounsaturated fat; 194 milligrams cholesterol; 25 grams carbohydrates; 5 grams dietary fiber; 196 milligrams sodium (does not include salt to taste); 14 grams protein