Pre-heat the oven at 180 °. Grease a 18cm x 18cm baking dish or pan.
Use a food processor to blend the oats, sugar, cocoa powder and salt until very fine.
Sweet potato puree should be made with the baked potato. Cut into large pieces and place to bake, remove and mash to make the puree
Add the sweet potato puree, peanut butter and vanilla extract, beat again until the ingredients are well blended. The dough is creamy, dense and heavy.
remove the blade from the processor and add the chocolate chips and the chopped walnuts
spread the dough in the prepared pan, set aside and bake until firm, with a crispy crust on the outside, but still moist on the inside, around 20 to 25 minutes
Wait a few minutes before unmolding and let it cool completely before slicing.