To make the marinade, put all the ingredients in a large shallow dish and mix well. Place the steak in the marinade, then cover and refrigerate for 30 minutes, turning the slices over after 15 minutes so that both sides absorb the flavours.
Meanwhile, put the rice in a saucepan, add 3 cups (750ml) water and bring to the boil. Cover and simmer very gently for about 20 minutes or until the rice is tender and has absorbed all the water. Remove from the heat.
Put all the ingredients for the dressing in a large salad bowl and whisk to combine. Add the rice to the bowl and stir gently to mix with the dressing.
Preheat the grill to medium. Remove the steak slices from the marinade and place on the rack of the grill pan. Grill for 5–6 minutes or until cooked to your taste, turning over halfway through the cooking and brushing with any remaining marinade. Transfer the steak to a board and cut the slices across the grain into thin strips. Add to the rice.
Just before serving, add the papaya, spring onions and salad leaves and toss gently together. Sprinkle with the sesame seeds and serve.