Melt dark chocolate in a microwave-safe bowl in 30-second intervals until smooth, about 1 minute. Set aside to cool slightly.
Combine avocados, melted chocolate, dark cocoa powder, honey, and salt in a food processor. Grind instant coffee to a fine powder and add it. Blend until smooth and creamy, scraping down the sides as needed.
Add the coconut milk to the food processor and blend again until completely smooth and creamy. Spoon the mousse into serving glasses and refrigerate for at least 1 hour, or preferably 3-4 hours.
When ready to serve, melt 2 tablespoons of coconut oil in a skillet over medium heat.
Add the sliced bananas to the skillet and cook for 2 minutes on each side, until nicely browned and caramelized.
Spoon the warm caramelized bananas over the chilled mousse and serve immediately.