In a large bowl, mix mashed sweet potatoes and melted butter.
Add flour, brown sugar, baking powder, and salt. Mix well until a soft dough forms.**
Add the raisins and mix until incorporated.
Turn the dough out onto a well-floured surface and knead it a few times until the dough is solid enough to roll out.
Roll the dough ½ inch thick and cut the cookies with a cookie cutter (heart shaped is traditional). Place the cut cookies onto a parchment lined baking sheet. Re-roll and cut any remaining dough, until all the dough has been used.
Bake the cookies for 12-15 minutes, until firm and slightly springy when touched.
Remove the cookies from oven and let them cool on the pan for 5 minutes.
Remove the cookies from the baking sheet to finish cooling on a wire rack.
Notes
*To make mashed sweet potatoes, peel and quarter a medium sweet potato (roughly ½ lb). Place it in a saucepan and cover it with water. Cover the pan and bring the water to a boil. Boil the peeled sweet potato for 30 minutes, or until easily pricked with a fork. Once cooked, drain and mash the potato with an electric hand mixer, until smooth.You will need ½ cup of mashed sweet potatoes for 1 dozen cookies.**Depending on the moisture level of your mashed sweet potatoes, you may need to add a little water (or water from boiling the sweet potatoes) to your dough to achieve a good consistency.