Spiced Sweet Potato Mash

Fill and boil your kettle, and preheat the oven to 200°C (Gas Mark 6). Fill a large saucepan with the boiled water from the kettle, place over a medium heat and add both sweet and baking potatoes, boiling them for about 8 minutes or until easily pierced with the tip of a sharp knife. Tip the cooked potatoes into a colander to drain, then sit the colander back on top of the hot, empty pan so that the potatoes dry a little more in the residual heat. Put the potatoes back into the pan, then add the 75g of butter, plus the ground coriander, cinnamon, sugar and lime juice. Season well with salt and pepper, then mash everything together until smoothly combined. Butter the bottom and sides of a large oven-proof dish, then tip in the potato mixture and dot the top with a little more butter. Bake in the hot oven for about 15 minutes, or until golden on top and properly hot throughout. Scatter with the fresh coriander to serve.