In a medium bowl, whisk together the eggs and granulated sugar until pale and slightly thick, about 2-3 minutes. Heat heavy cream in a saucepan over medium heat until just beginning to simmer.

Gradually pour the cream into the egg mixture while whisking continuously to temper the eggs for a smooth base.

Chop bittersweet chocolate into small pieces and place it in a large heatproof bowl. Pour the tempered egg and cream mixture over the chocolate, stirring gently until glossy and smooth.

Divide the mixture among serving cups, cover with plastic wrap and refrigerate for at least 4 hours, ideally overnight.

Before serving, prepare a dollop of espresso cream on top and sprinkle with flaky salt.