For the broth, preheat the broiler on high. Place the onion and ginger on a foil-lined sheet pan and cook them until they are slightly charred, about 5 minutes per side. Rinse with water.
In a large saucepan over medium-low heat, toast the cinnamon, anise and coriander for a few minutes until fragrant. Add the stock, soy sauce, carrots and charred onion & ginger. Bring to a boil, reduce heat to simmer, cover and cook for 30 minutes. Strain the broth.
While the broth is cooking, make the rice noodles according to package instructions.
To serve, divide the broth, noodles and toppings between 2 bowls.