Put the potatoes in a preheated oven and bake them for about 30-45 minutes, until you can push a skewer through them easily. Let them cool, then scoop out the flesh.
Pour boiling water over the spinach in a bowl, let it wilt, then drain. Allow to cool, then squeeze out the water.
Put the sweet potato flesh into a mixing bowl, add the spices, egg, garlic, coriander leaves and the grated halloumi.
When the spinach is cool, chop it finely and add to the bowl.
Chop the spring onions too and add to the bowl.
Mix everything together. Season with salt and pepper then fold in enough gram flour to get a thick, mouldable dough.
Using your hands, form the mixture into 4 big or 8 small balls, then press them into patties.
Coat the patties in the remaining gram flour then fry them in hot oil over a medium heat until golden on each side, turning once. Alternatively bake them in a pre-heated oven.
Serve warm or at room temperature.