In a small saucepan, heat the water together with the sugar until they come to a boil.
Remove from the heat and add the couverture, finely chopped into small pieces.
Mix with a hand whisk until it melts completely and a smooth chocolate syrup is formed.
Then optionally add the cognac, continuing to mix, and let the mixture cool for approximately 10 minutes.
Crush the rusks and the hazelnuts.
Add them to the chocolate syrup and mix gently with a spatula until all the ingredients are combined.
Cover the bowl and place it in the refrigerator until the mixture cools and firms up.
Once the mixture is ready, shape small balls in the size of your choice and coat them evenly with chocolate sprinkles.