Slice the sweet potatoes length ways in half, and place in an oven dish. Rub a small amount of oil on the cut surfaces, then place in the oven, 200°C.
In a pot with a lid that can be placed in the oven, toast the buckwheat over a low heat with the tablespoon of butter or oil. Stir constantly to toast the buckwheat evenly, for about 5 minutes. Add the boiling water, stir quickly then put the lid on and place in the oven for about 20 minutes, or until the water has been absorbed.
When the sweet potato is soft, remove from oven and mash into the buckwheat. Add the spices, lime juice and season to taste with salt and pepper.
When the mixture is cool, form into patties with wet hands, and pan fry with coconut oil for a few minutes on each side, until browned and heated through. Keep warm in oven while you finish cooking the patties, and serve with tomato chutney and salad, or with flatbreads as wraps. *