Heat the oil in a wok over a high heat until the oil starts to shimmer. Add the black bean sauce and stir-fry for a few seconds, then add the sliced beef and stir-fry for about 1 minute until half-cooked.
Mix in the chilli, onion and yellow peppers and stir-fry for 1–2 minutes. Then add the hot stock and bring to the boil.
Stir in the cornflour paste slowly until the sauce has thickened and become transparent. Serve immediately.