Dissolve the espresso powder in 1 tablespoon of boiling water. Set aside.
Break the egg into a small bowl, remove the yolk into a medium bowl, and pour the whites into the stand mixer bowl. You can use an egg separator to help. If an egg breaks, don’t use it...just get a new egg.
Place the chocolate in a medium microwave-safe bowl and melt in a microwave on HIGH, stirring after each 30-second increment, until smooth. Let it cool slightly. Stir in the olive oil, espresso, vanilla extract, and salt until combined. Set aside.
Place the egg yolks and ¼ cup sugar in a medium bowl and whisk until pale yellow. Add to the melted chocolate and stir until smooth.
Beat the egg whites in the bowl of a stand mixer fitted with a whisk attachment (or with a hand mixer) until soft peaks form. Gradually sprinkle in the remaining ¼ cup sugar and beat just until stiff peaks form.
Add a generous spoonful of the egg white mixture to the chocolate mixture. Stir firmly until completely incorporated. Pour the chocolate mixture into the bowl of egg whites. Gently fold with a large spoon or rubber spatula until completely combined.
Divide the mousse into six 4-ounce ramekins and cover with plastic wrap. Refrigerate at least 4 hours or overnight.
To serve, garnish with a light sprinkling of cocoa nibs and/or sea salt. Serve and enjoy!
Using dark chocolate (60 to 72% cacao) will result in a richer chocolate flavor, but you can use semisweet if you want to back off on the intensity. Whichever you choose, try to use the best chocolate you can.Same is true for the olive oil...use the best olive oil you have, one whose flavor you enjoy. It's time to break out the good stuff here, people.Note that this mousse contains raw eggs. If you're concerned about the risks of eating raw eggs, you can use pasteurized eggs without affecting the resultsSeparate the eggs carefully, no yolk can be in with the egg whites because the fat will keep the whites from whipping into a meringue.The recipe doubles easily, and can be made up to three days ahead.