Coarsely chop the pistachios.
Whip the egg whites until foamy.
Add erythritol and vanilla extract, then mix further.
Add the chopped pistachios and almond flour and mix together.
Pour the batter into a mold.
Bake in a preheated oven at 180°C (356°F) for 20 minutes.
Let it cool completely, then cut into bite-sized pieces.