Cook the noodles: Bring a pot of water to a boil and cook ramen noodles according to the package. Drain, then toss them with 1–2 teaspoons oil to keep them from sticking. Set aside.
Start the broth: In the same pot, heat the oil over medium heat. Add the onion and cook 5–7 minutes until soft and lightly golden. Add the garlic and ginger. Cook for 1 minute.
Pour in chicken stock, soy sauce, and mirin. Bring to a gentle simmer.
Poach the chicken: Season chicken with salt and pepper, then lower it into the broth. Poach gently until cooked through, about 12 to 18 minutes. Remove the chicken to a plate and let it rest.
Finish the broth: Turn the heat to low. Ladle ¼ cup of the hot broth into a small dish and whisk in the miso until smooth. Pour the miso mixture back into the pot. Add the toasted sesame oil and chili paste, if using. Taste and adjust the seasoning, then keep the broth warm over low heat while you sauté the mushrooms.
Sauté the mushrooms: In a skillet over medium-high heat, sauté the mushrooms with a bit of oil and a pinch of salt until browned, 5–7 minutes.
Assemble the ramen: Divide the noodles into bowls. Ladle the broth over the noodles. Slice the chicken and add it to the bowls. Top with the sautéed mushrooms, pickled carrots, and green onions. Add the soft boiled eggs, and nori then finish with a drizzle of toasted sesame oil. If you like it spicy, add a drizzle of chili paste or sriracha.
Notes
Poach chicken in the broth: This keeps the chicken tender and juicy while infusing the broth with extra flavor. No need for a separate skillet or extra cleanup.Dissolve miso separately: Whisking miso with a ladle of hot broth first helps it dissolve smoothly. Adding it straight to the pot can leave you with clumps and uneven flavor.Keep heat low after miso: Miso is delicate. High heat can dull its savory, umami flavor. Once it’s in the broth, keep the heat just warm, not boiling.Cook noodles separately: Boil the ramen noodles in a separate pot and toss them with a bit of oil to prevent sticking. This keeps the texture just right and stops them from soaking up too much broth.Customize toppings: Classic options like soft-boiled eggs, mushrooms, green onions, and nori are great, but feel free to use what you have. Spinach, pickled veggies, or leftover roasted vegetables all work.