We will be using only one pan to stir fry each ingredient separately to have maximum control over their texture and color.
Place a pan over medium to low heat. Add 1 tsp cooking oil, turn and tilt to fully coat surface.
First, fluff the egg whites, mix in a pinch of salt and pepper. Pour egg whites into hot pan, tilt the pan to thin egg whites out.
When done with one side, flip over to cook the other (~ 2 minutes). Transfer egg whites to a flat surface (e.g. cutting board) for cooling.
Repeat the above steps but using for egg yolks instead.
Next is sweet onion and scallion. Add a spoon of oil to hot pan if need. Then add sweet onion and a pinch of salt, saute for 2 minutes then add in scallion.
Stir to mix and remove from pan. Do not overcook or you get mushy onion.
Add bean sprout and a pinch of salt, stir fry for 2-3 minutes till they're wilt a little. Remove from pan.
Repeat above step to stir-fry carrot sticks, just make sure to remove them when they're still crisp.
Do the same thing to stir fry bell pepper.
Bring pan back to medium heat, 1 tsp oil if need, otherwise just add garlic, brown a little then stir in spinach. Add a dash of sea salt and keep stirring till when they're wilt a little, remove from heat.
Strain off liquid, save it to add to mushroom later if desire.
Now add 1 tsp oil if need, stir in the marinaded mushroom w/ their sauce and everything. Stir fry for 2-3 minutes until they're fully cook. Transfer to container.
Add in the marinaded beef fillet with sauce and all. Keep stirring while cooking to even them out for 2-3 minutes. When they're medium-done, transfer to a container to let them rest and cook themselves.
Add 1 Tbsp oil, make sure pan is coated well. Now add the marinaded dangmyeon along with their sauce.
Keep stirring until all the sauce was absorbed, and the noodle becomes sort of sticky.
Remove from pan and divide into serving bowls.
Then divide and add each of the stir-fried ingredients used into sections on top of the noodle.
Thinly slice egg whites and yolks and garnish on top.
Sprinkle on some roasted sesame seed atop to decorate and serve.
To Eat: mix everything in the bowl as you eat them. Enjoy