Heat vegetable oil in a large pot over medium heat. Add minced garlic and chopped onion. Sauté until the onion is translucent and fragrant.
Add sliced ginger and cook for another 1-2 minutes.
Pour in the chicken or vegetable broth. Stir in the fish sauce, soy sauce, sugar, and white pepper. Bring to a boil, then reduce the heat and let it simmer for about 10 minutes to allow the flavors to meld.
If using dried rice noodles, cook them according to the package instructions. If using fresh noodles, add them directly to the pot.
Add the cooked chicken or pork, bean sprouts, and baby spinach (or herbs) to the soup. Simmer for an additional 2-3 minutes, or until the noodles are tender and the vegetables are cooked.
Enjoy your meal!