01 - Combine beef slices with soy sauce, mirin, sesame oil, and cornstarch in a bowl. Let marinate for at least 15 minutes at room temperature.
02 - Bring a pot of water to a gentle boil. Carefully lower eggs and simmer for exactly 6½ minutes. Transfer immediately to an ice bath to stop cooking, peel once cooled, and set aside.
03 - Heat vegetable oil in a large saucepan over medium heat. Add minced garlic and grated ginger; sauté for 1 minute until fragrant. Stir in chili paste and miso paste, cooking for another minute to develop flavors.
04 - Pour in stock, soy sauce, rice vinegar, and brown sugar. Bring to a simmer and cook for 10 minutes to allow flavors to meld together.
05 - Prepare ramen noodles according to package instructions. Drain thoroughly and set aside, keeping them warm.
06 - Heat a separate pan over high heat. Quickly sear marinated beef for 2-3 minutes until just cooked through. Remove from heat immediately to prevent overcooking.
07 - Add sliced mushrooms and julienned carrots to the simmering broth. Cook for 3 minutes until vegetables are just tender-crisp.
08 - Divide cooked noodles evenly among four serving bowls. Ladle hot broth with vegetables over noodles. Arrange seared beef slices, halved soft-boiled eggs, baby spinach, spring onions, sliced chili, sesame seeds, and nori strips on top.
09 - Serve ramen piping hot while broth remains steaming. Enjoy immediately for best texture and temperature.