Heat half the sesame oil in a large casserole dish over a medium heat then add half of the sliced onion and sweat for 4-5 minutes, stirring occasionally. Add the chilli, star anise, red pepper and beef stock to the pan and bring to a simmer.
Add the coconut milk and bring back to a simmer. Simmer for 10 minutes.
Meanwhile, rub the steak with the remaining sesame oil and season lightly. Heat a heavy-based frying pan over a high heat until smoking hot then sear the steak all over. Add to the soup base along with the basil leaves, rice noodles and beansprouts.
Simmer for 8-10 minutes until the noodles are cooked. Remove from the heat and adjust the seasoning if necessary. Stir in the remaining onion and the mint leaves and remove the steak from the dish.
Slice very thinly into strips and return to the dish. Spoon into serving bowls and serve immediately.
This recipe is perfect for making in large batches and freezing to use at a later date.
In order to enjoy optimum flavour and quality, frozen items are best used within 3 months of their freezing date.
Always defrost and heat thoroughly before eating. Never re-freeze food that has already been frozen; this includes raw and cooked ingredients such as meat, fish and poultry.
For top tips on protecting you and your family when preparing raw meat and poultry, visit Food Safety in the Home and view the full Food safety at home video.