7 1/2ouncesgood quality semisweet chocolate, melted and cooled slightly
1 1/2ouncesall-purpose flour
2tablespoonsinstant espresso powder
Digital kitchen scale
Whipped cream charger and nitrous oxide cartridge
Whisk the eggs, sugar, and salt in the bowl of a stand mixer for 1 1/2 minutes on medium-high speed. Add the melted chocolate, flour, espresso powder, and vanilla, and whisk on medium speed for 30 seconds.
Pour 2 cups of the mixture into a whipped cream charger, filling only halfway. Charge with 1 nitrous oxide cartridge. Shake 10 to 15 times. Dispense the foam into coffee mugs until 1/3 full.
Place 1 mug at a time in a microwave. Cook for 45 seconds at 90-percent power. Repeat with the remaining batter. Serve the cakes immediately.