Aromatic Pork and Noodle Soup

Name: Aromatic Pork and Noodle Soup
Ingredients: 1 medium onion, peeled, halved through root end; 2 chiles de árbol or ½ tsp. crushed red pepper flakes; 2 garlic cloves, crushed; 1 cinnamon stick; 2 star anise pods; 1 teaspoon fennel seeds; 1 1” piece ginger, peeled, crushed; 8 cups low-sodium chicken broth; 2 tablespoons vegetable oil; 2 bone-in pork shoulder steaks (about 12 oz. each); Kosher salt and freshly ground black pepper; 8 ounces thin rice stick noodles; Mung bean sprouts, fresh cilantro leaves with tender stems, thinly sliced scallions, chopped unsalted, roasted peanuts, and lime wedges (for serving)