Make the dashi broth. Pour 2 quarts of water in a large pot along with the dried shiitake mushrooms and konbu. Cover and bring to a boil over high heat. Reduce the heat to low and continue to simmer for 10 minutes. Turn off the heat, add 1 cup bonito flakes, and cover the pot. Let the broth sit for 10 minutes. Strain the broth, reserving the mushrooms and discarding the bonito flakes and konbu. Thinly slice the mushrooms and set them aside.
Slice the scallions, separating the white stems from the green tops. Heat 1 tablespoon oil in a large pot over medium-high heat. Saute the grated garlic, ginger, and white stems of the green onions until aromatic, about 1 minute. Add 6 cups of the prepared dashi broth along with the reserved shiitake mushrooms. Cover and bring to a boil.
Season the broth with 2 tablespoon mirin, 2 tablespoon sake, 1 ½ teaspoon soy sauce, ¼ cup white miso, 2 tablespoon ground sesame seeds, and ground white pepper to taste. Add the sliced carrots, napa cabbage, and tofu and cook until the vegetables are tender, about 7-8 minutes.
Add the ramen noodles and enoki mushrooms and cook until the noodles are cooked. Remove from heat and garnish with the green tops of the scallions. Serve the miso hot pot with ponzu for dipping sauce if desired.