Cook the whole potatoes until done but not too soft - about 20 minutes - then drain and cool.
Coarsely grate the cooked potatoes into a bowl and gently sprinkle the spice mix and salt through as you grate.
Heat the butter and oil in a heavy-based pan and let the foam subside.
Place the potato mix into the pan, either in several fritter-sized cakes or as one large cake, being careful not to press down too hard.
Cover with a lid and cook over medium heat for 6-8 minutes, until the underside has browned. Gently turn the cake or cakes over, and cook a further 5-6 minutes until they are cooked through and browned.
Remove the pan from the heat and slide the potato cake/s onto a warmed serving dish.
Cut into pie-wedges and serve with salad.
Salt is added to this recipe as there is no salt in the Herbie's Spices version of Ras el Hanout. If you use a different spice mix, you may not need to add salt if there is salt in the spice mix.