In a medium saucepan, whisk together 4 large egg yolks and 1/2 cup granulated sugar until pale and creamy. Heat 2 cups heavy cream in a separate pot until it begins to simmer, then gradually pour into the egg mixture while whisking constantly.

Chop 8 ounces of bittersweet chocolate and place it in a bowl. Pour the warm custard mixture over the chocolate and let sit for 1 minute. Whisk until smooth.

Distribute the chocolate mixture into jars or ramekins, cover with plastic wrap, and chill in the refrigerator for at least 4 hours.

Prepare the topping by whipping heavy cream with a spoonful of espresso powder until soft peaks form. Spoon onto each budino and sprinkle with flaky sea salt.