Create a double boiler. Fill a pot halfway with water and bring to a simmer, not a boil. Fit a bowl over the top, making sure the water doesn't touch the bottom of the bowl.
Add your chocolate to the bowl. Continue to stir until the chocolate is melted. Allow it to cool.
Add your egg whites to a bowl. Use a hand mixer to beat it until it forms stiff peaks and holds its own shape.
Add one yolk at a time into the cooled chocolate, whisking continuously. If the mixture becomes too thick drizzle a little cream in.
Add the orange juice and zest into the chocolate mixture and stir to combine.
Add a big spoonful of the egg whites into the chocolate mixture and stir vigorously. This will loosen the chocolate mixture.
Add the remaining egg whites. Use a spatula to gently fold them into the chocolate.
Divide the chocolate mousse between four ramekins or serving glasses. Allow it to chill in the refrigerator for at least 2 hours.
To serve, top with whipped cream and chocolate shavings.