Such big flavor dividends for a small investment

How can a soup be both filling and light, easy yet complex? That's what I wondered when I first made and tasted the Caldo of Sweet Potato and Chard in Jason Wyrick's new book, “Vegan Mexico.” The answer, at least in this case, is about the ingredients: few in number, but carefully chosen for big impact.

As you might expect from a Mexican soup, much of the flavor comes from chilies. In this soup, it's dried ancho chilies, which I seed so the heat level isn't so much a punch as a gentle, warming burn. The chilies make the broth; they get pureed into their own cooking water, seasoned only with garlic, salt and oregano. The result is a brick-red soup whose taste is reminiscent of mole but with a fraction of the effort. The broth is just thin enough to not seem weighty, while cubes of sweet potatoes and some pinto beans add satisfying heft.

I figured Wyrick wouldn't steer me wrong. He's the source of some of my favorite taco fillings, including griddled plantains and charred zucchini, both of which I found revelatory.

The revelation here is simple: that I could feel so warmed and satisfied by something this low in calories and fat, and that a soup this quick to come together could taste as if it had simmered all day.

• Joe Yonan is the Food and Dining editor of The Washington Post and the author of “Eat Your Vegetables: Bold Recipes for the Single Cook.” Follow him on Twitter @JoeYonan.