Cook the ramen noodles according to package directions, omitting the liquid seasoning packet.
Before draining, reserve about 1/2 cup of the starchy cooking water. Drain the noodles well.
In a small bowl, whisk together the egg yolk, Parmesan cheese, garlic powder, and black pepper. Set aside.
Return the drained noodles to the pot (off the heat). Add the butter and stir until melted.
Pour in the heavy cream and mix quickly to coat the noodles.
Remove the pot from the heat completely. Immediately pour in the egg yolk and cheese mixture. Stir vigorously and continuously. The residual heat will cook the egg into a creamy sauce without scrambling it.
If the sauce is too thick, add the reserved pasta water, one tablespoon at a time, until you reach a smooth, creamy consistency.
Stir in half of the liquid sauce packet from the ramen seasoning. Taste and add more seasoning as desired for heat level.
Serve immediately, topping with an extra sprinkle of Parmesan cheese if you like.
Notes
For the best creamy texture, make sure the pot is off the heat when you add the egg yolk mixture.
If you prefer a milder spice level, use the original Buldak sauce packet instead of the 2x Spicy version.
This recipe works well with other instant ramen brands if you substitute the Buldak sauce packet for your preferred spice base.