The key to good stir-fried kangkong is a very hot wok. If too much is cooked in one go, the wok wouldn't be hot enough. Hence, this recipe is for 250 g kangkong, which is only 150 g or so after trimming the roots. That's enough for 2 portions. If you need to make more, I suggest stir-frying the sambal in one go, then the kangkong in batches.
Trim and discard kangkong roots. Wash and drain. Chop 8 cm (3 inch) long. Press thick stems between fingers to break stem walls.
Trim dried chillies. Soak in water till soft, about 30 minutes. Drain and discard water.
Soak dried prawns in 1 tbsp water till soft, about 15 minutes. Drain, reserving soaking liquid.
Toast belacan till fragrant.
Wash and roughly chop chilli and bird's eye chillies. Peel, wash and roughly chop shallots and garlic.
Grind dried chillies, dried prawns, belacan, bird's eye chillies, shallots and garlic into smooth paste.
In a very hot wok, stir-fry sambal in vegetable oil over high heat till fragrant. Add salt and sugar. Stir through. Taste and if necessary adjust seasoning. Add kangkong and stir-fry till just wilted, 30 seconds or so, drizzling with the water for soaking dried prawns towards the end. Taste again and adjust seasoning if necessary.