Into a microwave-safe bowl, add Dark Chocolate (100 gram). Heat in the Panasonic Microwave Oven for 1-2 minutes, stopping every 30 seconds to stir, until completely melted and smooth. Set aside to cool.
Into a large mixing bowl, add Whipping Cream (300 milliliter). Using an electric mixer on medium speed, beat for 2 minutes, until mixture forms soft peaks.
Add Nutella® (3/4 cup). Beat to combine.
Drizzle cooled dark chocolate over the top. Use a metal spoon to swirl it around and fold gently together. Don't mix it together completely; you want the swirls of chocolate to show.
Transfer mousse into serving glasses. Garnish with Chocolate Shavings (to taste). Serve immediately, or chill for a couple of hours before serving if you prefer a firmer mousse. Cooking results may vary depending on microwave oven used.