Preheat the oven to 350°F (175°C). Grease and flour a 9x9-inch (or 9–10-inch round) baking pan and set aside.
Bring about 3 cups of water to a gentle boil in a small saucepan.
Put 1 cup cold coconut cream and 8 oz (1 cup) vegan dark chocolate chunks in a heatproof metal or glass bowl. Set the bowl over the saucepan so it sits above the boiling water (do not let the bowl touch the water). Stir frequently until the chocolate and coconut cream have melted and the mixture is smooth, about 5 minutes. Remove the bowl from the heat and let the mixture cool until lukewarm.
In a small bowl, dissolve 2 tsp Ener‑G egg replacer in 3 tbsp water; stir until fully combined. In a separate small bowl, mix 1 tbsp flax meal with 2 tbsp water and let it sit until slightly thickened (about 5 minutes).
In a large bowl, combine 1 overripe banana (mashed), the Ener‑G mixture, the flax mixture, 2 tsp vanilla extract, 1 tsp instant espresso/coffee powder, and 1 cup sugar. Stir until well combined.
In a medium bowl, whisk together 1 cup unbleached all‑purpose flour, 1/2 tsp salt, and 1 tsp baking powder.
Pour the cooled chocolate–coconut mixture into the bowl with the banana/wet ingredients and stir to combine. Gradually add the flour mixture, stirring until just combined; the batter should be fairly wet.
Pour the batter into the prepared pan and smooth the top. Arrange the 1 ripe banana, sliced thinly lengthwise, on top of the batter.
Bake at 350°F for about 40 minutes, or until a toothpick or paring knife inserted near the center comes out with a few moist crumbs (not wet batter).
Remove the brownies from the oven and let them cool in the pan on a wire rack for 30–40 minutes before cutting.