Prepare the Flavor Base: Combine grated garlic, ginger, and horseradish with turmeric, vinegar, oil, and salt until a fragrant paste forms.
Heat the Broth Base: Bring 8 cups of water to a gentle boil, then reduce heat to a soft simmer.
Mix the Miso: Whisk miso paste with hot water until smooth and lump-free.
Combine and Infuse: Turn off the heat, whisk in the miso mixture, lemon juice, and zest until golden and aromatic.
Serve Warm: Ladle into bowls, garnish with scallions, and serve immediately.
