- 180gr high-quality chocolate (60-70% cacao is ideal)
- 1/3 cup plus 2 tablespoons whole milk
- 1 tablespoon instant espresso powder
- 1 egg yolk
- 4 egg whites
- Pinch cream of tartar
- 2 tablespoons sugar
- 1/4 tablespoon salt
Chop chocolate into small pieces and place in a bowl large enough to contain all of the ingredients and accommodate the folding process. Place the bowl over a bain marie or a simmering water bath. Make sure the bowl is not touching the water and the water is kept to a simmer. Take off the heat when the chocolate is melted.
Gently bring the milk to a boil and whisk in the espresso powder until it is completely dissolved. Pour over the melted chocolate and slowly whisk. Add the egg yolk and whisk until fully incorporated.
Whip egg whites on medium speed until they reach medium peak stage. Increase speed to high and gradually add sugar in a slow steady stream until egg whites are firm and glossy.
Using a large rubber spatula, add 1/3 of whites to chocolate mixture and gently whisk to combine and lighten. Gently fold in remaining 2/3 egg whites until there are no streaks. Portion into individual servings or a large bowl. Chill for 45 minutes before serving for peak texture, or up to two days.