Using the smallest blade on a spiral slicer, spiralize daikon into long, thin, spaghetti-like strands. For best results, trim the strands with kitchen scissors once they reach about 10-12” long. Place trimmed strands on clean paper towels or kitchen towels to absorb excess moisture and set aside.

Add oil to a large, heavy-bottomed pot over medium-low heat. When hot, add onions and stir until coated. Cook approximately 45 – 50 minutes, stirring every 5 minutes or so to ensure they cook evenly and don’t stick to the pan. The exact cooking time will vary based on several factors, including the age of the onions and how thick you cut them.

Once the onions are caramelized and a rich golden brown, reach the desired depth of color, add 3 tablespoons bone broth to deglaze the bottom of the pan. Add more if necessary to scrape up all the brown bits, then season with salt to taste.

Add mushrooms, herbs, and garlic powder to the pot and saute until tender, about 5 minutes. Add remaining broth to skillet and simmer over medium-low heat until heated through, about 10 – 15 minutes.

Increase heat to medium and add daikon “noodles.” Cook for another 5-6 minutes and season with salt to taste.

Ladle soup into individual serving bowls and garnish with sliced green onion. Serve immediately.