Preheat the oven to 180°C convection oven and line a rectangular baking tin (approx. 32cm x 24cm) with baking paper so that it overhangs the sides slightly.
Prepare the egg substitute: Mix the flax seeds with 120 ml hot water and leave to soak for 5 minutes.
Place the chocolate and coconut oil in a heatproof bowl and melt slowly over a water bath.
In a bowl, mix together the ground almonds, porridge, cocoa powder, baking powder, salt and sugar.
Add the swollen flax seeds, chocolate mixture and 80ml hot water and mix briefly with a dough scraper or wooden spoon until all the ingredients are combined.
Pour the batter into the prepared tin and smooth it out.
Coarsely chop the hazelnuts and then spread them evenly over the dough.
Bake the dough for approx. 35 min. and then leave to cool for at least 20 min.
Then carefully remove from the baking mould and cut into 12 pieces.