Heat a large saucepan over med-hi heat. Add oil to pan; swirl to coat. Add shallots; cook 1 minute, stirring frequently. Add garlic and ginger; cook 30 seconds, stirring constantly. Add broth; bring to a boil, scraping pin to loosen browned bits. Add lemongrass and 2 cups water to broth mixture; bring to a boil. Reduce heat; simmer 10 mins. Stir in chicken and spinach; simmer 5 mins. Discard lemongrass. Remove from heat; stir in cilantro, basil, lime juice, and salt. Place 1/2 cup noodles in each of 4 bowls; top each serving with 1 1/2 cup soup. Sprinkle with red pepper.