Preheat the oven to 180°C (350°F). Line a 20 cm (8-inch) square baking pan with baking paper.
Add the chocolate and milk to a small saucepan over medium heat. Melt until combined. Add the cooked sweet potato and almond butter and use a stick blender to puree the mixture until as smooth as possible (or use a food processor / stand blender). Set aside to cool slightly.
Add all the dry ingredients to a large bowl and mix until there are no lumps. Add your chocolate mixture and mix until combined. The brownie batter should be thick and fudgy.
Scoop the brownie batter into your baking pan and smooth the top.
Optional: sprinkle the extra chocolate and walnuts/pecans on top and gently press them into the batter.
Bake the brownies for 15-20 minutes (shorter if you like fudgy brownies, longer for crispy brownies). The brownies are ready when you can insert a skewer into the middle and and there are only some crumbs on your skewer. Keep in mind that the brownies will set more over time! Allow the brownies to cool in the baking pan.
When you are ready to serve the brownies, remove them from the pan, slice and enjoy!
Store the brownies in an airtight container at room temperature up to 1 day, in the fridge for up to 1 week or in the freezer for up to 1 month.