Preheat oven to 350°F.
Combine 1 to 1½ tablespoons of flax meal with 3 tablespoons water to make the flax egg. Let sit for 10 to 15 minutes.
Combine chickpeas, banana, flax egg, cacao powder, dates, and vanilla extract in a food processor (or blender) until fully combined and smooth.
Fold in ¾ cup of nut mixture and 1 tablespoon coconut flakes (and optional nibs). Coat an 8-by-8-inch baking pan with coconut oil and fill with batter. Top with ¼ cup nuts and 1 tablespoon coconut flakes.
Bake in the oven for 30 to 45 minutes. Let cool and cut into 9 brownies.