In a large pot, heat the vegetable oil over medium-high heat. Add the sliced beef and cook until browned, about 3-4 minutes. Remove the beef from the pot and set aside.
In the same pot, add the minced garlic and grated ginger. Sauté for about 1 minute until fragrant.
Pour in the beef broth and water, bringing the mixture to a boil.
Add the sliced mushrooms and soy sauce to the pot. Reduce heat and let simmer for 5 minutes.
Stir in the instant ramen noodles and cook according to package instructions, usually about 3-4 minutes.
Add the cooked beef back into the pot along with the baby spinach. Cook for an additional 2 minutes until the spinach is wilted.
Drizzle with sesame oil and season with salt and pepper to taste.
Serve hot, garnished with chopped green onions and a soft-boiled egg if desired.