If sweet potatoes are not already cooked, then cook them before starting. Either pierce the potato and microwave it until tender (about 8 minutes), or roast in the oven at 400 for about 30-40 minutes until cooked through. Once cooked, allow to cool, then remove the skin and mash the flesh.
Preheat the oven to 350 F. Grease an 8x8" glass baking dish and set aside.
In a large mixing bowl, combine the mashed sweet potato, nut butter, vanilla, eggs, almond milk, and coconut sugar. Use an electric mixer to mix until everything is well-combined.
Add the dry ingredients, mix well, and then fold in the chocolate chips, if using.
Pour batter into greased dish and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
Once done, remove the brownies from the oven and allow them to cool completely before frosting.
Meanwhile, make the frosting: combine all ingredients in a food processor and blend, stopping to scrape down the sides if necessary. Add additional almond milk if mixture is too thick.
Spread frosting over cooled brownies and then cut into bars.
