Make brownies: Preheat oven to 350ºF; grease an 8-inch square baking pan.
In a food processor, combine avocados, maple syrup and coconut sugar; blend until smooth. Add eggs; pulse to blend. Add cacao, collagen, almond flour, baking powder, baking soda, salt, vanilla and instant coffee (if using); blend until well combined and smooth. Add chocolate chips and swirl in with a spatula.
Transfer batter to baking pan, spreading evenly. Bake until just set in the middle, 25 to 30 minutes. Let cool in pan on a wire rack, then cover and refrigerate for at least 1 hour.
Make frosting: In a high-speed blender or food processor, combine all ingredients. Start with 2 Tbsp. maple syrup. Blend until smooth. Taste and add more maple syrup, if needed. (Yield: About 1 cup)
When brownies are thoroughly chilled, spread frosting on top. Sprinkle with a topping, if desired, then cut into 12 bars and serve. Cover and refrigerate any leftovers.