- Fry the beef strips in oil over a high heat. Once cooked, pour the soy sauce into the pan and cook for a further minute.
- Spread the mustard onto both slices of bread.
- Lay 4 of the tomato slices, on 1 of the slices of bread.
- Top with beef strips and cover with second slice of bread.
- Pop the sarm on a heated pan and toast until outside of bread is golden. Remove from heat and fill with fresh baby spinach.
- Slice and skewer to serve.