Cook the noodles according to the packet instructions, drain, rinse and set aside.
Heat a large non-stick frying pan or wok and heat 1tbsp of the oil in the pan. Add the onion, carrot and pepper. Cook for 1-2 minutes, stirring occasionally. Add the kale or chard and cook for 2-3 minutes. Stir through the noodles.
Meanwhile preheat the grill to moderate.
Add the mango, lime zest and half the juice to the pan. Toss gently. Season and set aside.
Put the steaks on a chopping board, season and rub with the remaining oil on both sides. Cook the steaks for 1-2 minutes on each side. Leave to rest on a warm plate, then cut into slices and toss into the noodle salad.
Spoon the salad onto a warm plate, drizzle with the remaining lime juice and serve immediately.