Trim off any fat and cut beef into small bite size pieces.
Place vermicelli noodles in a large bowl and cover with hot water to soften – set aside. Note some people prefer to use cold water.
In the largest pot you have, add 2 tablespoons of oil and sauté onion, garlic and ginger over a medium heat. Once softened add 1 more tablespoon of oil and the beef pieces and cook until meat is just cooked through. This might take 10-15 minutes.
Once meat is cooked through, add 1 cup of water and then enough soy sauce to cover the meat. Cook for 5-6 minutes
While meat is cooking cut the vermicelli with kitchen scissors so they are in shorter pieces, and then drain.
Add vermicelli one handful at a time to the beef and stir well after each addition. Keep stirring so that it doesn’t catch on the bottom. This helps the vermicelli brown evenly.
Once all vermicelli is added, add more water (1-2 cups) so the sapasui looks wet but not soupy.
Cover and cook for 5-6 minutes, stirring often so it doesn’t burn. The finished sapasui should not look dry or watery but somewhere in between.
Optional: towards the end of cooking, add the chopped spring onion and capsicum.
Taste and add more soy sauce if needed.