Stock - You can use vegetable or fish stock
Sweet Soy (Kecap Manis) Is something I use often but you can just use extra soy sauce and a teaspoon of honey if you want a little extra sweetness. Or leave out altogether.
Pak Choy replacements – If you want to stay on theme you can use gai larn, bok choy or wong bok. But Broccoli, carrots and spinach would also be lovely.
Use a pinch of salt if you don’t have fish sauce
Make this dish your own, its just a base and I have tried to use really simple ingredients to make it achievable, and for a wide range of palates. But go crazy, use chilli oil, fry off some onions first, add lemongrass stalks. The world is your oyster with this one. Ohhh Oyster Sauce would be good too, add a glug of this. You get my drift!