Separate the egg whites from the egg yolks. Place the egg whites into a large bowl (of a stand mixer if you have one), and set the egg yolks aside.

Using an electric mixer with beaters or a whisk attachment, beat the egg whites for several minutes until they triple in size. Slowly stream in the sugar, and continue to beat the eggs until the mixture is glossy and very stiff; peaks should stand up on their own.

Meanwhile (or right after this if you have a handheld mixer), break the chocolate into pieces and place into a microwaveable bowl. Microwave the chocolate for 30 seconds, stir, then repeat until the chocolate is nearly melted (don't skip any stirring or the chocolate may burn). Remove the chocolate from the microwave and continue stirring for 1-2 minutes to completely melt the chocolate and let it cool slightly.

When the egg whites are finished and the chocolate has cooled just a bit, stir the egg yolks quickly into the chocolate to continue to cool the mixture without cooking the eggs. Add ⅓ of the egg white mixture to the chocolate and gently stir to combine.

Scoop the chocolate mixture into the mixing bowl with the rest of the egg whites. Carefully fold the chocolate into the egg whites several times, moving slowly and gently, until the mousse is smooth and nearly uniform in color.

Transfer the chocolate mousse to small serving dishes, and into the refrigerator. Chill for at least two hours or up to overnight.

Serve topped with whipped cream, extra chocolate shavings, and berries, if desired.

Enjoy!