Melt chocolate in double boiler (bain-marie) or in microwave for 30 seconds. Add eggs, sweeteners, and vanilla and mix until smooth. Add the flour and chopped nuts.
Put in a Pyrex mold with parchment paper or a little oil and bake in a preheated oven at 355ºF (180°C) for 20-25 Minutes or until it starts to firm up. Allow to cool and that’s it!