Make the Broth:

Prepare the following, adding each to a large pot or Dutch oven as you complete it: Coarsely chop 1 large yellow onion (do not peel). Coarsely chop 2 medium scallions. Dice 5 ounces daikon (do not peel, about 1 cup). Halve a 2-inch piece of ginger lengthwise, then smash with the flat side of your knife. Remove 2 cloves from a head of garlic (leave the rest of the head intact) and set aside for the garlic oil; cut the remaining head of garlic in half horizontally through the middle.
Add 10 cups water and 5 dried shiitake mushrooms to the pot. Bring to a boil over medium-high heat. Reduce the heat to maintain a simmer and cook for 15 minutes. Meanwhile, make the tare.
Make the Tare:

Place 1/4 cup plus 2 tablespoons soy sauce in a small saucepan and bring to a simmer over medium heat. Remove the saucepan from the heat. Add 1 tablespoon white miso paste and 1 tablespoon nutritional yeast and whisk to combine. Add a 1×2-inch piece of kombu and set aside to steep for at least 20 minutes.
When the broth is ready, remove the pot from the heat. Add a 4×4-inch piece of kombu and 2 tablespoons nutritional yeast and stir to combine. Let steep for at least 20 minutes. Meanwhile, make the garlic oil and prepare the remaining ingredients.
Make the Garlic Oil:

Finely chop the reserved 2 garlic cloves. Place in a small skillet and add 4 teaspoons neutral oil. Cook over medium heat, stirring constantly, until the garlic starts to turn brown, 60 to 90 seconds. Remove the skillet from the heat. Continue stirring until the larger pieces turn golden brown, 15 to 30 seconds more. Immediately scrape into a small heat proof bowl, add 2 teaspoons toasted sesame oil, and stir to combine.
Prepare the Remaining Ingredients:

Remove the large outer leaves from 4 small heads baby bok choy and reserve; halve the bulbs lengthwise. Drain and cut 1 (about 14-ounce) block of tofu in half lengthwise, then cut crosswise into 1/2-inch thick slices. Finely chop 4 medium scallions. (If your broth is almost ready, bring a large pot of water to a boil over medium-high heat.)
When the broth and tare are done steeping, transfer the shiitake mushrooms to a cutting board. Trim the stems and thinly slice the caps if they’re tender (discard if too chewy). Pour the broth through a strainer set over a large bowl; discard the contents of the strainer. (You should have about 8 cups of broth.) Return the broth to the pot and place over medium heat. Add 1/4 teaspoon kosher salt and 1/4 teaspoon MSG if desired and stir to combine.
Pour the tare through the now-empty strainer directly into the pot of broth and whisk to combine. Reduce the heat to low to keep the broth hot.
Cook the Bok Choy and Noodles:

If you haven’t already done so, bring a large pot of water to a boil over medium-high heat. Add the bok choy bulbs and cook for 30 seconds. Add the bok choy leaves and cook until wilted, 15 to 30 seconds more. Use a slotted spoon or spider to transfer all the bok choy to a bowl or plate.
Return the water to a boil. Add 24 ounces fresh ramen noodles or 18 ounces dried instant noodles and cook according to package directions. Drain and divide between 4 bowls. Stir the broth and ladle over the noodles. Top with the bok choy, tofu, scallions, and mushrooms. Drizzle with the garlic oil. Garnish with toasted sesame seeds and togarashi powder if desired.