In a medium mixing bowl, add all ingredients. Mix with a spatula until cocoa powder and maple syrup are completely incorporated into the peanut butter and the batter is uniform in color. The batter will be very thick, almost like cookie dough. Taste and adjust as needed. If you prefer sweeter you can add 1-2 tbsp more syrup (but know your batter will not be as firm) and if you want more chocolate flavor you can add 1 more tbsp of cocoa.
Add batter into lined loaf pan and evenly press and spread it across the pan with your hands or with a spatula. Use your spatula to help smooth the surface. While the batter can be eaten right away, I like putting it into the fridge to firm up a little more. If desired, you can also spread a frosting on top. Place brownies into fridge to set for about an hour. This will let it firm up more, making it easier to cut and eat. When brownies are set, lift them from the baking pan by grabbing the ends of the parchment paper. Slice into squares with a sharp knife. Store uneaten brownies in the fridge.
Notes
Make sure to use natural peanut butter with no added oils. The brownies will not set if you use peanut butter with added oils.
Make sure to use maple syrup and not honey. Maple syrup helps the brownies set and it will not set the same with honey.
The frosting is not necessary but it does make these taste even more brownie-like as well as adding more texture and flavor.
Optional chocolate frosting: If you want to use the frosting I made in the photos, you will need 1/4 cup melted coconut oil, 1/2 cup unsweetened natural cocoa powder (dutch process does not work) or cacao powder, and 1/4 cup maple syrup.
First mix the coconut oil and cocoa powder until smooth. Then stir in the syrup until incorporated and the frosting thickens.
The nutrition information provided are only estimates based on an online nutritional calculator. This is not a comprehensive list of all the nutrients in the recipe (i.e., does not include vitamins, cholesterol, etc). I am not a certified nutritionist. Please consult a nutritionist or doctor for accurate information and any dietary restrictions and concerns you may have.