Boil noodles for 3 minutes (or 1 minute less than packet instructs).
Meanwhile, whisk together the noodle sauce packet, Kewpie mayo, and egg in a large bowl until well combined.
Add Momofuku Spicy Seasoned Salt and stir. (We add 1 tablespoon, but if you prefer less salt, start with 1 teaspoon and you can add more at the end.)
Drain noodles, reserving 1 cup of piping hot water.
Immediately whisk hot water into your mayo mixture, adding gradually at first to keep eggs from scrambling.
Once all your water is added, toss in the noodles.
Top with spinach, chicken, and scallions.
Adjust the seasoning with more Momofuku Spicy Seasoned Salt, as needed.
Make your ramen more savory with a few shakes of Momofuku Soy Sauce or spicier with a spoon of Momofuku Chili Crunch.
Serve immediately.
