For the eggnog brownies, cut the butter and chocolate into small pieces and melt them together slowly in a saucepan.
Beat the eggs and sugar well, then slowly stir in the chocolate-butter mixture. Finally, fold in the flour, baking powder and hazelnuts.
Mix the cream cheese with the eggnog and a whole egg until well blended.
Pour the mixture into a round baking pan lined with parchment paper and smooth it out. Spread the eggnog cream cheese on top and mix lightly with a wooden spoon. Bake the eggnog brownies in a preheated oven at 170°C for about 20 to 25 minutes.