Roast your sweet potatoes in the oven, I did mine at 400 for about 30 minutes (time will large on the size of your sweet potatoes). Allow them to cool until they are warm to the touch and then peel the skins off and place them in your blender. Melt your chocolate in the microwave (or double boiler if you prefer), and pour the chocolate into the blender. Add your vanilla and blend until smooth. Spread in an 8x8 pan and place in the fridge until chilled. If you want it to be extra chocolate-y melted some extra dark chocolate, drizzle it on top, and chill again.