Heat the oil in a large saucepan over high heat until hot. Reduce the heat to medium, add the onion and cook, stirring occasionally, until softened, about 5 minutes. Add the salsa and cook, stirring, for 5 minutes. Add the chicken broth and simmer, partially covered, for 10 minutes. Add the chicken and hominy and simmer until heated through. Add salt and pepper to taste. To serve: ladle into bowls and let everyone garnish their own portion. Mexican Tomatillo Salsa: Combine the 3 fresh tomatillos, husked, rinsed, and quartered, 4 scallions (white and light green parts), coarsely chopped (about 1/2 cup), 1/3 cup coarsely chopped cilantro (stems and all), 2 tablespoons vegetable oil, 1 tablespoon fresh lime juice, 1/2 jalapeno or 1 Serrano chile, seeds removed, if desired, 1 small garlic clove, minced (3/4 teaspoon) in a food processor and pulse until the ingredients are almost smooth with a few small chunks. Add kosher salt and freshly milled black pepper to taste. Cover and refrigerate until ready to serve. Makes a scant 1 cup.