Chop the dark chocolate and put it in a bowl. Fill a small saucepan halfway with boiling water, place it on the stove, and place the chocolate bowl on the pan. In this way, melt the chocolate in a bain-marie.

Remove the melted chocolate from the heat and add the tahini to it. Add the walnuts. Add vanilla and cardamom. Finally, add a pinch of salt and mix well.

Get a different bowl with the exact dimensions. Cover the bottom of the bowl with cling film. Pour the chocolate mixture over it. Finally, cover this bowl tightly with another cling film. Put it in the freezer and leave it for at least 6 hours.

Take the frozen vegan chocolate cake that has been in the freezer long enough out of the freezer. Keep it at room temperature for 5 minutes.

Remove the cling film at the top. Take a flat plate and turn the bowl upside down. Also, remove the cling film from the base. Cover it with cocoa powder by sprinkling it generously.

For a good presentation, optionally sprinkle dried rose petals or cocoa powder. Serve by slicing the dessert.