Peel the sweet potatoes. Cut them into chunks and place into a steamer for about twenty minutes, until they become really soft.
Once they are perfectly soft and beginning to fall apart, remove them and add them to a food processor with the apple puree. Blend until a smooth, creamy mix forms.
Put oats baking powder, flour, cacao and sugar into a bowl. Add the sweet potatoes. Stir well.
Placet he mix into a baking dish with baking paper and bake for about 30 minutes. After 20 minutes baking time cover the brownies with aluminium.
Let cool completely before you cover the brownies with peanut butter. Then melt the chocolate and spread it over the brownies.
Place the brownies in the refrigerator and chill for 1 hour (and up to 4 hours or even overnight) to set the chocolate. The Brownies taste even better on the following day!