In a large pot, heat vegetable oil over medium heat.
Add minced garlic and grated ginger to the pot and sauté for 1-2 minutes until fragrant.
Pour in chicken broth and water, then bring to a simmer.
Add sliced shiitake mushrooms and cook for 3 minutes until slightly tender.
Stir in soy sauce and miso paste until the miso is fully dissolved.
Add the ramen noodles to the pot and cook for 3-4 minutes until noodles are just tender.
Slowly stir in the heavy cream and baby spinach, cooking for an additional 2 minutes until the spinach wilts and the broth becomes creamy.
In a small bowl, whisk the egg.
Temporarily reduce heat to low and slowly drizzle the whisked egg into the pot while stirring gently to create egg ribbons.
Remove the pot from heat and stir in sesame oil and crushed red pepper flakes.
Ladle the creamy ramen into bowls and garnish with sliced green onions before serving.