Preheat oven to 325°F (163°C). Place six 6-ounce ramekins in a deep roasting pan and set aside.

Heat heavy cream in a medium saucepan over medium heat until it just begins to steam and tiny bubbles form around the edges, about 5 minutes. Remove from heat and whisk in espresso powder until completely dissolved.

In a large bowl, whisk together egg yolks, 1/3 cup sugar, vanilla extract, and salt until smooth and pale yellow, about 1 minute. Do not overbeat or create excessive foam.

Slowly pour the warm espresso cream into the egg mixture in a thin stream, whisking constantly to temper the eggs. Strain the mixture through a fine-mesh sieve into a large measuring cup with a spout.

Divide the custard evenly among the prepared ramekins, filling each about three-quarters full. Carefully pour hot water into the roasting pan until it reaches halfway up the sides of the ramekins.

Bake for 35-40 minutes until the custards are set around the edges but still jiggle slightly in the center when gently shaken. The centers should look barely set, not liquid.

Carefully remove ramekins from the water bath using tongs and let cool on a wire rack for 30 minutes. Cover each with plastic wrap and refrigerate for at least 4 hours or up to 2 days.

Just before serving, remove custards from refrigerator and pat the tops completely dry with paper towels. Sprinkle 1 tablespoon of granulated sugar evenly over each custard in a thin layer.

Using a kitchen torch held 3-4 inches away, caramelize the sugar in circular motions until it melts and turns deep amber. Let the sugar harden for 2-3 minutes before serving.