While waiting for the water to boil, prepare the sirloin: Pat it dry, chop into cubes. Mix in bowl with salt and pepper, minced garlic and ginger.
Heat the oil in a skillet over medium-high heat. When the skillet is smoking, add the steak cubes and cook for three to five minutes on all sides. Set aside to rest.
Once the water is boiling, add both types of noodles and cook until just-tender, four to five minutes.
Strain the noodles, reserving four to five tablespoons of the starchy water.
Return noodles to the pot over low heat and add the Chapagetti and Neoguri seasoning packets, and the reserved noodle water. Stir until the seasonings are well blended.
Add steak cubes to the noodles. Mix well.
Plate the noodles and steak in a bowl, top with scallions.
