01 - Combine beef slices with soy sauce, sesame oil, Sriracha, garlic, and black pepper in a bowl. Let stand for at least 15 minutes to absorb flavors.
02 - Combine chicken or beef broth, miso paste, soy sauce, mirin, chili oil, ginger, and green onion whites in a large pot. Bring to a simmer over medium heat, cover, and gently simmer for 20 minutes.
03 - Melt butter in a saucepan over medium heat. Add minced garlic and sauté until fragrant, about 1-2 minutes. Reduce heat, add heavy cream and cream cheese, stirring until smooth. Add soy sauce and season with salt and pepper. Simmer gently for 3-4 minutes, then remove from heat.
04 - Heat a large skillet or wok over high heat. Quickly sear the marinated beef for 2-3 minutes until just cooked through. Remove from heat and set aside.
05 - Boil ramen noodles according to package instructions. Drain well and divide among serving bowls. Arrange halved soft-boiled eggs, bean sprouts, spinach, and seared beef over the noodles.
06 - Ladle hot broth into each bowl. Drizzle creamy garlic sauce generously over the top. Garnish with sliced green onions, toasted sesame seeds, and sliced red chili if using. Serve immediately while hot.