Whisk the oil, soya sauce, curry powder and peanut butter together.
Heat a large frying pan over a high heat and add oil mixture.
When it starts to bubble, add the beef strips and vegetables.
Stir-fry over a high heat until cooked, but still crisp.
Add the nuts and season to taste.
Stir in the coriander if using and serve with noodles or rice.
For a vegetarian option, replace the beef strips with 200g cubed, smoked tofu. Serve on a bed of basmati rice.