For the potatoes, I went with Yukon gold because I like their buttery taste and because they hold their shape when cooked, unlike high-starch, thick-skinned baking potatoes. However, any potato will do as long as you cut it into 1-inch chunks. If the only spuds you have on hand are baking potatoes (such as russets), just be sure to peel them first. Otherwise, the skin will be too chewy in the soup.
There's very little fat in this recipe. The vegetarian version uses just 2 tablespoons of extra-virgin olive oil and half an ounce of grated Parmigiano-Reggiano. A little bit of that justly celebrated cheese goes a long way. And carnivores can keep the fat content low by trimming off the prosciutto's fat.
What's that? The little Mario Batali devil on your shoulder insists that the flavor will go bye-bye along with the fat? I was thrilled to discover that if you briefly bake the prosciutto on a rack in the oven, it becomes bacon-esque — crisp, salty and redolent of pork. Be sure to pull the prosciutto out of the oven before it is completely crisp. It will continue cooking even outside the oven. If it doesn't reach the desired state within a minute or two, slide it back into the oven and give it another quick jolt.
Now you've got all the flavor you — or your inner Mario — could ask for. Just keep an eye on the salt in the rest of the recipe. The cheese and the meat are high in sodium.Start to finish: 1 hour (40 minutes active)
2 tablespoons extra-virgin olive oil, divided
1 cup finely chopped yellow onion
1 tablespoon minced garlic
1 pound Yukon gold (or other thin-skinned potatoes), cut into 1-inch chunks
4 to 5 cups low-sodium chicken or vegetable broth
1/2 cup dry white wine
6 cups packed torn kale leaves
6 cups packed baby spinach leaves
1 teaspoon red pepper flakes, or to taste
1/4 pound thinly sliced prosciutto
Twelve 1/2 -inch-thick diagonally cut slices of baguette
1/2 ounce finely grated Parmigiano-Reggiano cheese
Heat oven to 400 F.
In a large saucepan over medium, heat 1 tablespoon of oil. Add onion and cook, stirring occasionally, until softened, about 5 minutes. Add garlic and cook, stirring for 1 minute. Add potatoes, 4 cups of stock and wine. Bring to a boil, cover pan and simmer for 10 minutes.
Add kale, cover pan, then simmer for another 10 minutes. Add spinach and pepper flakes, cover, and simmer for another 5 minutes.
Working in 2 batches, transfer about 3 cups total of soup solids with a little added broth each time, to a blender and puree until smooth. Be careful, hot foods expand in the blender. Return puree to saucepan, add salt to taste and additional cup of stock if necessary to achieve desired texture. Heat until hot.
Meanwhile, set a wire rack over a rimmed baking sheet. Arrange prosciutto slices in a single layer on rack, then bake on oven's middle rack for 10 to 12 minutes, or until they begin to crisp. Remove rack from sheet pan and set it on counter to let prosciutto cool. When cool, crumble prosciutto.
Arrange baguette slices in single layer on sheet pan and brush them with remaining tablespoon of olive oil. Bake them on oven's middle shelf until golden brown, 8 to 10 minutes. Sprinkle grated cheese evenly over them, return slices to oven and bake until cheese is just melted, 1 to 2 minutes.
To serve, ladle soup into 4 bowls, then top each portion with some prosciutto crisps and 3 toasts on the side.
Nutrition information per serving: 630 calories; 120 calories from fat (19 percent of total calories); 13 g fat (3 g saturated; 0 g trans fats); 25 mg cholesterol; 96 g carbohydrate; 8 g fiber; 5 g sugar; 31 g protein; 1,640 mg sodium.