Le Gâteau Martiniquais

The sweet potatoes used in this cake are the white type, either red or white skinned, called boniatos. They are true sweet potatoes, but are less sweet and have firmer flesh than the orange sweet potato, known as Louisiana yam, which may also be used. The term yam is mistakenly used, since yams and sweet potatoes come from entirely different botanical families. If the Louisiana yam is used, the cake will need longer cooking time.