In a bowl mix together all the spices. Then in a ovenproof dish pour in some olive oil. Add to the oil the washed potatoes and stir it around coating the potatoes with oil then repeat with the spices. At this point at the onions and chillis. Cover with tin foil and pop in the oven for 30 mins at 180 (fan). After the 30 mins remove the foil stir around check the oil hasn’t dried out then put back in oven for a further 10 mins.