Preheat the oven to 300ºF. Arrange six (4 ounce) ramekins in a shallow roasting pan; set aside. Bring a kettle of water to a boil.
In a medium saucepan, heat the cream, chocolate and espresso powder together over medium heat, stirring frequently until the chocolate is melted and the cream is steamy hot, but not simmering. Remove from the heat and whisk until smooth.
Meanwhile, whisk the yolks, ¼ cup of the sugar, the vanilla, and the salt together in a medium bowl. Whisking constantly, slowly pour the hot cream mixture into the yolk mixture. Pour the combined mixture through a strainer into a liquid measuring cup with a pourable spout.
Evenly pour the chocolate mixture into the ramekins. Fill the pan with enough hot water to come up the sides of the ramekins (being careful not to get any water in the custard).
Bake for 30 to 35 minutes or until the custard is set. Remove the ramekins from the water and cool to room temperature on a wire rack. Refrigerate until well chilled, at least 4 hours or overnight.
When ready to serve, sprinkle the tops with the remaining ¼ cup of the sugar (about 2 teaspoons per custard cup). Using a kitchen torch, heat the sugar until melted and golden, being careful not to warm the custard too much. Serve immediately or refrigerate until ready to serve. Enjoy!