Set a large soup pot or Dutch oven on the stove over medium heat so it is ready when the vegetables are prepped.

Cut the tofu into 1/2-inch cubes if you have not already, and keep it on a plate or cutting board near the stove.

Brown the tofu: Add the oil to the pot. When the oil looks loose and shiny, put the tofu cubes into the pot in a single layer.

Cook the tofu for 3 to 4 minutes, until the bottoms are lightly golden.

Turn the tofu with a spatula and cook for 3 to 4 minutes more, until several sides are golden. Transfer the tofu to a plate.

Put the mushrooms and carrots into the same pot. Cook over medium-high heat for 4 to 5 minutes, stirring a few times, until the mushrooms shrink and the carrots begin to soften.

Start the broth: Add the scallion whites, ginger, and garlic to the pot. Stir for 1 minute, until the mixture smells fragrant.

Pour the vegetable broth into the pot. Scrape the bottom of the pot with a wooden spoon to loosen any browned bits.

Turn the heat to high and bring the broth to a gentle boil.

Put the miso in a small bowl. Ladle about 1/2 cup of the hot broth into the bowl and stir until the miso is smooth.

Add the rice noodles to the pot. Stir once so the noodles separate in the broth.