In a blender jar, combine the torn guajillo chiles, tomatoes, onion, garlic, spices, oregano and 1 cup of the chicken broth. Blend as smooth as possible. (A food processor will work though it won’t completely puree the chile.)
In a medium-large (4- to 6-quart) heavy pot, heat the oil over medium-high. Set a medium-mesh strainer over the top and pour in the chile mixture. Press the mixture through the strainer into the hot oil. Cooking, stirring, until the mixture is reduced to the consistency of tomato paste, about 5 minutes.
Whisk the masa harina into the remaining 3 cups broth, then pour into the cooked chile mixture. Whisk until the sauce comes to a boil and thickens to the consistency of a light cream soup. Reduce the heat to medium-low. Add the chicken, green beans, chayote, or potatoes and 1 teaspoon salt. Simmer gently, stirring regularly, for about 20 minutes, until all the chicken and vegetables are tender.
Add the hoja santa or cilantro, then taste and season with salt, usually between 1/2 and 1 teaspoon, depending on the saltiness of your chicken broth, and serve.
Riffs on Yellow Mole: Because I have such respect for kitchen tradition (and the fact that I’ve already taken a few liberties with this revered classic here), I’m hesitant to go much further. I will say, however, that a seafood version of yellow mole is one of my favorite things in the world. When the vegetables have cooked for 10 minutes, in place of the chicken add a dozen or so mussels or clams and about ¾ pound firm-flesh fish (like halibut, bass or grouper) cut into about ¾-inch pieces. In Oaxaca, they also make a much thicker version of this sauce (they would add the equivalent of about 6 tablespoons of masa harina versus the 2 I’ve called for here) to use as a filling for what they call empanadas: They press out a corn tortilla from the prepared corn masa, lay it on a griddle to brown lightly, then flip it and top it with a spoonful of the thick sauce, a few shreds of cooked chicken and a big piece of hoja santa leaf. After folding it in half, the cook cooks the empanada on the griddle until toasty and aromatic.