Cut beef into strips that are ~ 5mm thick, 1cm wide and about 5cm long (1/5" x 2/5" x 2"). If using shortribs, trim excess fat, cut the meat off the bone. Then cut each piece in half lengthwise (to form 2 "steaks") then slice into 5mm thick. (See step photos in post or video at 0.11s, Note 6)

Marinate - Put beef in a bowl. Add marinade ingredients, then mix. Set aside marinate while you proceed with recipe, ~15 - 20 minutes is all it needs. (Note 5)

Sauce - Mix the Sauce ingredients in a very large mixing bowl.

Noodles - Cook sweet potato noodles per packet directions (normally 8 min in boiling water). Drain, briefly rinse under tap water then shake off excess water well. Add noodles into the bowl with the dressing. DO NOT MIX.

Batch 1 - Heat 2 tablespoons of oil in a large non-stick pan (30cm/12") over high heat. Cook the brown onion, white part of green onion and shiitake mushrooms with 1/2 tsp salt for 2 1/2 to 3 minutes, stirring constantly, just until starting to soften but not going golden. Pour on top of the noodles - don't mix yet!

Batch 2 - Using the same pan still on high heat, heat 1 tbsp oil then cook the carrot and capsicum for 1 1/2 minutes, constantly stirring. Add spinach, green onion and the final 1/2 tsp salt. Keep cooking for 1 1/2 minutes until the spinach is wilted. Transfer into the noodle bowl - still don't mix!

Cook beef - In the same pan, heat the final 1 tbsp of oil still on high heat. Add beef and cook for 1 1/2 minutes until very lightly golden and just cooked through. Add to the noodle bowl. Don't mix!

Mix! Add most of the sesame seeds (reserve some for topping). NOW you can mix! Toss, toss, toss.

Serve - Transfer into a serving bowl, sprinkle with remaining sesame seeds. This is meant to be eaten warm, not piping hot. Eat!