1. The light soy sauce adds the salt and the dark soy sauce adds a touch of colour. You can sub the dark soy with more light soy sauce, or just sub both the light and dark with ordinary soy sauce. The filling will just be a bit lighter in colour. Don't just use all dark soy sauce - flavour is way too strong - or with a thick sweet soy sauce like kecap manis.
2. Can sub with dry sherry or chicken broth.
3. Also great with chicken but I prefer pork because it's not as lean and has slightly more flavour. Chinese restaurants typically use pork. Never seen it with beef or lamb! Can also sub with 2 1/2 cups of chopped veggies of choice.
4. See in post for a photo of water chestnuts. These are a key ingredient in San Choy Bow as served at Chinese restaurants here in Australia. They have a natural light flavour, but it's the texture that is unique - a fresh crunchiness.
Nowadays these are sold in both the Asian and canned vegetable section of major supermarkets.
5. Typically served at Chinese restaurants using crisp iceberg lettuce leaves which are cut into neat rounds so they are all the same size. My preference is to use soft lettuce leaves like Butter Lettuce or Bibb Lettuce (US) because iceberg has a tendency to crack when rolled to eat, causing juices to run out. I used Baby Gem Lettuce in the photos which come in twin packs at Woolworths.
6. I use 3/4 cup of each vegetable (inc onion) so in total I use 2 1/2 cups of chopped vegetables. You can substitute with whatever chopped vegetables you want, though I urge you to stick with the onion.
The meat can be substituted with 2 1/2 cups of any vegetable or chopped firm tofu. For a super quick version, make this with pork + frozen diced vegetables. Works a treat!
This recipe makes enough for 3 as a main (4 if it's 2 adults and 2 kids) or around 6 as a starter.