1. Preheat the oven to 330°F (165°C). Grease a 7×7 inches square baking pan and line with a stripe of baking parchment. Set aside.

 

2. Add the butter and chocolate to a large microwave-safe bowl and melt – mix until well combined. Add the xylitol, cocoa powder, salt, and espresso powder and mix until well combined. If the mixture is still warm, let cool down a bit before you add the eggs. Add the eggs and vanilla extract and mix in. Mix the almond flour with the baking powder – add to the bowl and mix in. Add the chopped walnuts and fold in (optional). Transfer the batter to the prepared baking pan and smooth out the top. Bake for 25-30 minutes. Take out of the oven and let cool down completely. Remove from the pan, cut into 9 pieces and serve.