A few tweaks give chicken soup a spicy new attitude.
In a large pot of boiling salted water, cook noodles according to package instructions. Drain noodles. In a saucepan, combine chicken broth, lemongrass, ginger, and 3 cups water. Bring to a boil; reduce to a simmer, cover, and cook until fragrant, 10 minutes.
Using a fine-mesh sieve, strain broth and return to saucepan. Add chicken and snow peas and simmer until chicken is cooked through and snow peas are crisp-tender, 2 to 4 minutes.
Remove soup from heat and stir in lime juice. Season with salt and pepper. To serve, pour soup over noodles. Top with mint, lime wedges, and chile sauce if desired.
To release the citrusy flavor of lemongrass stalks, pound them with a meat mallet or a heavy pot. If you can't find fresh lemongrass, look for dried in the spice aisle.