The day before, prepare the sweet potato puree. Preheat oven to 400°F (200°C). Prepare a baking sheet lined with non-stick parchment paper. Set aside.
Prick two large orange sweet potatoes with a fork. Cut in half lengthwise, keep skin on. Place on a lined baking sheet, flesh side down, and bake for 30-45 minutes or until you can easily insert the tip of a knife into them.
Let them cool down for 20 minutes at room temperature, use a spoon to scrape out the flesh into a bowl, and mash with a fork. Refrigerate overnight in a sealed airtight container.
Preheat the oven to 350°F (180°C). Line an 8-inch x 8-inch pan with non-stick parchment paper. Set aside.
In a mixing bowl, add oats, sweet potato puree, peanut butter, maple syrup, and any optional ingredients you like for a boost of flavor. Stir with a rubber spatula a few times, until everything is very well combined, and it forms a thick, sticky batter.
Pour the batter into the prepared pan, press firmly with the back of a rubber spatula to form an even bar. Sprinkle chocolate chips on top if desired.
Bake the bars for 18-22 minutes at 350°F (180°C) until the sides are golden brown, and a toothpick inserted in the middle of the bar comes out clean.
Let them cool down in the pan, at room temperature, for 10 minutes, then for 2 hours on a cooling rack before slicing.
