Make the marinade by combining the plum sauce, white wine, cornflour, ginger, soy sauce and hoi sin sauce in a bowl. Whisk until combined.
Add the steak and kidney beans to the marinade. Cover with a lid or cling wrap and refrigerate for several hours or overnight.
Heat oil in a non-stick frypan or wok, add the steak mixture including the marinade, beans, mushrooms, capsicum and garlic.
Stir-fry until steak is lightly browned.
Add water, bring to the boil, simmer covered for a few minutes or until vegetables are tender. Serve.