Add the marinade ingredients to a large bowl and mix well, add the sirlion steaks, making sure they are well coated and then set aside to marinate for at least 20 minutes.
Meanwhile, slice the sweet potatoes longways into 4 thick slices, brush with a little oil, season with black pepper and bake in a hot oven for 15 minutes until golden and tender.
Heat a chargrill pan until very hot. Remove the steaks from the marinade and cook for 2 - 3 minutes on either side then remove the steaks from the pan, place onto a small plate, cover with tin foil and rest for 5 minutes.
Pour the remaining marinade into the pan with a little water and bring to a boil, reduce and simmer for a few minutes until the sauce is thick.
Meanwhile plunge the beans into hot water and boil for 2 minutes, then add the peas and cook for a minute before draining. Cut the rested sirloin steaks into slices.
Arrange the sweet potato slices onto warm plates, top with green beans, peas and slices of steak. Drizzle with sauce and scatter with chopped coriander and rocket leaves before serving.