The sweet potato is native to the tropical Americas, where they are known as yams. They are available in supermarkets all year round but are best between October and March. There are 2 main varieties; one with bright orange flesh, the other with a pale cream flesh.
Wash the sweet potato and peel the skin, if desired; it is possible to boil with or without the skin. Bring a large pan of water to the boil and dice into chunks. Once boiled, add the sweet potato to the water and leave to cook for 15-20 minutes, until tender. Remove from the heat, drain thoroughly and serve.
Preheat oven to 350F/180C/gas mark 4. Wash the sweet potato thoroughly, peel and cut into 1 inch chunks. Butter a rimmed baking sheet and transfer into the preheated oven until melted. Once the butter has melted, add the sweet potato chunks to the tray and roast for 45 minutes, until tender. Stir occasionally in order to ensure an even roast. Remove from the heat and serve.
Preheat grill to a high heat. Wash the sweet potato thoroughly and cut into wedges leaving the skin on. Season as desired. Place the wedges under the preheated grill for 3 minutes. Then flip the wedges and grill for a further 3 minutes. Reduce the heat to low and continue to cook for 20-30 minutes, until soft and tender and turning half way through. Remove from the grill and serve.
Wash the sweet potato thoroughly, peel and cut into 1 inch cubes. Bring 2 inches of water to the boil in a large pan under a steaming basket. Once the water has boiled, reduce to a simmer and add the sweet potato cubes to the tray. Cover and allow to steam for approximately 17 minutes, until tender. Remove from the heat and serve.
When frying sweet potato, it is best to parboil first. Wash thoroughly and add to a large pan of boiling water for 4 minutes. Remove from the heat and drain well before chopping into 2 inch slices. Melt a knob of butter in a large frying pan over a medium heat. Add sweet potatoes and fry until golden brown and fork tender, turning occasionally. Remove from the heat and serve.