In another bowl, whip the egg whites with sugar until you see soft peaks. Very gently fold whipped cream into the chocolate, then do the same with the egg whites until fully combined. Line a loaf pan with wax or parchment paper and pour in half of the mixture. Swirl 1/8 cup Nutella into the batter with a toothpick. Add remaining mixture, then swirl the rest of the Nutella into the top. Sprinkle crushed hazelnuts on top. Place in freezer for 4 hours or until ready to serve.