By SARA MOULTON
This soup is a stick-to-your ribs flexitarian special. Make it with chicken broth and prosciutto and you end up with a carnivore's delight. Make it with vegetable stock and no prosciutto and you've got a vegetarian's delight. Either way, it's plenty hearty. The potatoes give it body and creaminess. The spinach and kale give it earthiness and a bright green color.
The greens also happen to be nutritional superstars — both spinach and kale are terrific sources of vitamins A, C and K, not to mention fiber. For folks who generally find kale a little too assertive, the time to eat it is now, in the cooler months, when its taste is milder. And given kale's current "it" vegetable status, you'll certainly have no trouble finding it at the store. Some supermarkets even carry the bagged shredded leaves, as convenient as pre-washed lettuce or shredded slaw mix.
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? Not necessarily. I was thrilled to discover that if you briefly bake the prosciutto on a rack in the oven, it becomes downright bacon-esque — crisp, salty and redolent of pork. Just 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. Both the cheese and the meat are high in sodium.