Separate the egg yolks and whites into two different bowls, ensuring no yolk mixes with the whites.
3 Large Eggs
Place chocolate and butter in a heat-proof bowl. Melt in your microwave in 20 second increments at 50% power, stirring between each heating. Let cool slightly.
4 ounces Chocolate, bittersweet, 4 Tablespoons Unsalted butter
Add egg yolks and vanilla to the bowl. Whisk until well combined.
1 teaspoon Vanilla extract
Add ½ teaspoon salt to bowl of egg whites. Using an electric mixer with the whip attachment, begin whisking until whites become foamy.
Begin adding the sugar slowly while continuing to mix. Keep whipping the whites until stiff, glossy peaks are formed.
2 Tablespoons Granulated sugar
Fold the egg whites into the chocolate mixture in two additions. Using a rubber spatula gently fold after each addition taking care not to deflate the whites, but you also don't want any white streaks.
Place the bowl in the refrigerator for 20 minutes. Cover the bowl with plastic wrap if the batter will be in the refrigerator for more than a few hours.