Preheat oven to 160 °C.
Spread the almonds on a baking sheet and roast them for about 15 minutes turning frequently. Process them in a blender until finely ground.
Soak the prunes in the cognac for at least an hour and up to a day. Process in a blender until smooth.
Melt the chocolate in bain-marie or in the microwave and fold in the almonds and prunes. Mix well.
Let the mix cool a little bit and form small bite-sized balls.
Spread the powdered almond or sesame seeds on a large plate and roll around until coated.
Cover the truffles and put them in the fridge for an hour to firm up.
The truffles will keep in an airtight container for about a week.