Add one-third of the egg whites to the chocolate and stir them together.
You’re just looking to lighten the heaviness of the chocolate at this stage, so don’t worry about deflating the egg whites.
Then add the remaining egg whites and gently fold them into the chocolate.
You can do this by scraping your spatula in a circular motion around the outside of the bowl, lifting from the bottom to the top.
When you’re done, it should be pretty well combined but it’s also okay if there are still a few streaks in the batter.