Use leftover cooked sweet potato or bake one from scratch (see instructions above). Add the cooked sweet potato to a bowl and mash really well until you have a smooth purée.
Add the almond butter, cacao powder, honey and egg, then mix until fully combined. You can use a fork for this, but if you prefer an ultra-smooth texture, a hand blender works beautifully.
Transfer the mixture into a small baking dish lined with parchment paper. Fold in most of the dark chocolate chips, keeping a few aside to sprinkle over the top. Smooth the surface, then scatter the remaining chocolate chips on top.
Bake in a preheated oven at 180°C for about 30 minutes. If you prefer a gooier centre, remove the brownie from the oven around 5 minutes earlier. Once baked, lift it out using the parchment paper and allow it to cool completely on a wire rack before slicing.
