Put the chilli-garlic sauce, chopped onion, garlic and tomato purée in a food processor with 200ml water and blitz to a smooth paste.

Heat the oil in a large nonstick frying pan over a medium heat and fry the mince and sliced onion for 5-8 mins until the mince is browned. You may and it easier to do this in batches.

Stir in the chilli paste. Simmer over a low heat, stirring, for 10-15 mins until the mince is cooked through. Meanwhile, boil the green beans for 2-3 mins. Drain and set aside.

Add the black bean sauce and black beans to the beef, increase the heat to high and fry for another 5 mins until the sauce is reduced and glazes the beef and beans. Stir in the green beans and water chestnuts and cook for 1-2 mins more to heat through.