Chicken-and-Cheese Enchiladas

INGREDIENTS

• Pinch of sugar
• 1 small red onion, halved
• Kosher salt
• 1 to 2 serrano chile peppers, stemmed and seeded
• 3/4 cup crumbled queso fresco or feta cheese
• 3 cups shredded rotisserie chicken
• 1/2 cup low-sodium chicken broth
• 1/3 cup fresh cilantro
• 2 1/2 cups shredded mozzarella and/or Monterey Jack cheese
• 1 1/2 pounds tomatillos, husked and rinsed
• 2 tablespoons extra-virgin olive oil, plus more for greasing
• 8 corn tortillas