Chinese New Year Chicken Noodle Soup

Name: Chinese New Year Chicken Noodle Soup
Ingredients: 2 tablespoons peanut oil; 2 stalks lemongrass, chopped; 1 tablespoon fresh ginger, grated; 8 cups low sodium chicken broth; 1/4 cup rice vinegar; 1/4 cup low sodium soy sauce; 2 teaspoons brown sugar; 1 tablespoon Sambal Oelek (ground chili paste); 1 tablespoon Chinese 5-spice powder; 1 teaspoon black pepper; 3-4 skinless, bone-in chicken thighs; 8 ounces button mushrooms, sliced; 1 bok choy, chopped; juice of 1 lime; 8 ounces udon noodles; Shredded carrots, Fresno chiles, cilantro, green onions + toasted sesame seeds, for topping