Method

• Pre heat the oven to 180C.Roast the sweet potato on a baking tray for 45 minutes -1 hour or until it is tender in the centre and slightly caramelised on the outside.Towards the end add the pecan nuts to the tray and roast them for 5 minutes until slightly browned.Cool the pecan nuts and chop them up and set them aside.
• Prepare the baking tray 28cmx18cm by greasing it with the oil or butter if you prefer and set aside.You can also line the try with baking paper and then grease that baking paper.
• Remove the potatoes from the oven and let it cool, scoop out the flesh and make sure you have 200g, place it in a blender.
• Add the dates (stone removed )and blend them with the sweet potato until smooth.
• Break up the chocolate and place it in a double boiler or in a glass bowl over boiling water to melt the chocolate slowly.Stir a few times.
• Add the sweet potatoes to the melted chocolate.
• Add the oil and tahini and stir until smooth.
• Beat the eggs in a separate bowl and add the sugar slowly until the mixture is almost double in volume. 
• Whisk in the chocolate mixture until well blended.Fold in the1/3 of the pecan nuts.
• Scrape the mixture into the tin and scatter some of the remaining pecan nuts on the top.
• Bake for 25 minutes until it is nice and puffy and looks dry on top.
• Remove from the oven and cool, once cooled, slice into squares.
• Chill and they will keep for up to 3 days.Enjoy :)