Preheat oven to 325F and grease a 9x9 baking pan well. In a medium bowl, stir together ground chia seed and water. Let sit until thickened, about 10 minutes.
In a large bowl, whisk together the almond flour, sweetener, baking powder, and salt. Stir in egg, coconut oil, banana extract, vanilla extract and chia seed mixture until well combined. Stir in chocolate chips.
Spread batter in prepared baking pan and bake until just set, about 25 to 28 minutes. You don't want them to be dry, so don't over bake. Let cool in pan. The edges should pull away from the sides. Gently transfer to a piece of waxed paper or parchment paper to frost (I flipped them out onto my hand, then flipped them back over onto a piece of waxed paper).
Melt butter (or coconut oil) and peanut butter together in a medium microwave safe bowl. Whisk in sweetener until well combined. Spread over cooled bars.
Refrigerate to let the frosting set, about 30 minutes.
Serves 16. Each bar has 4.01g NET CARBS.Food energy: 226kcal Total fat: 19.87g Calories from fat: 178 Cholesterol: 7mg Carbohydrate: 8.25g Total dietary fiber: 4.24g Protein: 6.38g Sugar Alcohols (erythritol): 11.25g