Preheat the oven to 180°C. Get a square tray ready and linen with some parchment paper.

In a microwavable dish add the butter, dark chocolate pieces and both types of erythritol.

Melt on medium heat for 1 minutes, stirring constantly until the erythritol is completely dissolved.

Let it cool for a few minutes and add eggs, one by one, mixing well. Add the vanilla essence.

Add the flour and the cocoa through a sieve to ensure there are no lumps.

Once the mixture is well incorporated add it to the square tray.

Cook for 15min at 180° C, let it cool slightly before removing from the tray. Enjoy!