Soak 100g dates in hot water if needed (see note below).*
Peel and chop 700g sweet potato, then steam for 15-20 minutes until soft. Set aside to cool.
Preheat the oven to 180°C (fan)/200°C/gas mark 6. Grease a 20cm square baking tin and line with non-stick baking paper .
Place 100g dates in a blender or food processor and whizz into a paste. If you don't have a blender you can mash them using a pestle and mortar.
Add the cooked sweet potato and blend or mash together with the dates.
Put 50g ground almonds, 80g plain flour, 3 tbsp cocoa powder into a large mixing bowl and mix well. Add 3 tbsp maple syrup and the sweet potato/date mixture and stir together.
Transfer to your prepared baking tin and level the surface with a spatula or the back of a wooden spoon.
Bake in the oven for 30-40 minutes until you can insert a skewer in the centre and it comes out clean.
Leave in the tin for 10 minutes (this helps it to stick together) then remove and cut into squares. Cool completely on a wire rack then store in an airtight container for a few days.