1. Pierce the sweet potatoes with the fork and bake in the oven for 1 hour at 400F/200C. Cool the sweet potatoes for 10 minutes until they become easy to handle. Halve these and then coarsely chop, leaving the skins on.
2. Take the chopped sweet potatoes into a food processor and then add the rest of the ingredients, pulsing until the mixture is smooth, while adding up to 2 tbs. of water if required, to achieve the desirable consistency. Season with salt and pepper if desired and then serve at room temperature, garnishing with lime zest if using.