Preheat oven to 220 C. Put the diced potatoes in an ovendish and mix in the cumin, chili and the oil. Add salt and pepper to taste.
Roast the mix in the oven for about 40 minutes and then test the softness of the potatoes with a fork. If they are still undercooked, put them back in the oven until they fall from the fork.
In the meantime make a salad by mixing the sliced cabbage and grated carrot together. Sprinkle with salt and leave to drain in a sief.
Make a dressing by mixing the limejuice and orangejuice with the fishsauce. Add the ginger and sugar and stir well. Mix the dressing with the drained salad.
Put the chicken in a heated frying pan and caramelize the meat. After a few minutes add the onion and chili (if you like you can also add some finely sliced bell pepper). After a few minutes add the seasoning mix and stir well. Leave on a low heat for a couple of minutes more, so the flavors can mix in the dish.
Serve the fajitas with all the sidedishes, so everybody can assemble his own personal mexican taste bomba