Heat the vegetable oil in a heavy deep saucepan or large wok over medium heat. It will be ready when a wooden stick inserted will bubble at a nice pace; not too fast.
Fry the cashew nuts for about five minutes until they are golden brown. Use a skimmer to take them out onto a paper towel lined plate.
Fry the dried chillies for just 10 seconds or so, until they release their aroma. Don't let them burn.
Put chillies and cashews in a bowl and toss with salt to taste. Sprinkle with spring onions.