Place the dried kelp in a small bowl and pour warm water over it. Let soak for 15 minutes until softened and pliable. Remove and set aside, reserving the soaking water.
Add the kelp soaking water to a large pot with 1.5 liters of fresh water. Bring to a gentle simmer over medium heat, maintaining around 80°C (176°F), and keep it simmering while preparing other ingredients.
Slice the shiitake mushrooms thinly. Heat vegetable oil in a skillet over medium heat. Add the mushrooms and cook for 5-7 minutes, stirring occasionally, until they release a fragrant aroma and turn a deep brown around the edges.
Add the browned mushrooms directly to the simmering broth. Stir in soy sauce and miso paste, then let everything simmer uncovered for another 20 minutes. The broth will deepen in color and aroma, filling your kitchen with earthy, briny scents.
Meanwhile, cook the ramen noodles in boiling water according to package instructions, usually 2-3 minutes, until just al dente. Drain and set aside.
Gently fold the cubed silken tofu into the simmering broth during the last 5 minutes, allowing it to warm through without breaking apart. The broth should be fragrant, rich, and slightly opaque with a velvety texture.
Taste the broth and adjust seasoning as needed with more soy or miso. Once ready, ladle the hot broth with mushrooms and tofu over the cooked noodles in bowls.
Finish each bowl with a drizzle of toasted sesame oil and garnish with sliced green onions for a fragrant, bright touch. Serve immediately while hot, enjoying the savory aroma and vibrant presentation.
