Toss the beef strips with 2 tablespoons of the soy sauce, 1 teaspoon of the sugar, and half the garlic. Let it sit while you cook everything else.
Make the egg ribbons. Heat a little of the neutral oil in a nonstick pan over medium-low and pour in half the beaten egg, swirling into a thin sheet. Cook gently with no browning, about 1 minute, flip, then slide out. Repeat, then roll both sheets and slice into thin ribbons.
Boil the glass noodles 6 to 7 minutes until chewy but not mushy. Drain, rinse under cold water, snip a few times with scissors so they are forkable, and toss with 1 teaspoon of the sesame oil.
Blanch the spinach for 30 seconds, rinse cold, and squeeze it firmly dry.
Stir fry the onion and carrot with a pinch of salt in the same pan over high heat for 2 minutes, then remove. Add the remaining neutral oil and stir fry the beef for 2 to 3 minutes until just cooked.
In your largest bowl, combine the noodles, beef with its pan juices, vegetables, and spinach. Add the remaining soy sauce, sugar, garlic, and sesame oil, and toss thoroughly with tongs. Fold in the egg ribbons last so they stay intact, and finish with sesame seeds. Taste; it should be glossy, savory, and lightly sweet.