Preheat oven to 325°F (160°C). Place four 6-ounce ramekins in a deep baking dish and bring a kettle of water to a boil for the water bath.

Heat the heavy cream in a medium saucepan over medium heat until it just begins to steam, about 3-4 minutes. Remove from heat and whisk in the sifted matcha powder until completely smooth with no lumps visible.

In a separate bowl, whisk together the egg yolks, 1/3 cup sugar, and salt until pale and slightly thickened, about 1 minute. Slowly pour the warm matcha cream into the yolk mixture while whisking constantly to temper the eggs.

Stir in the vanilla extract. Strain the custard through a fine-mesh sieve into a large measuring cup or bowl to remove any bits of cooked egg.

Divide the custard evenly among the four ramekins. Carefully pour the boiling water into the baking dish until it reaches halfway up the sides of the ramekins.

Bake for 35-40 minutes until the edges are set but the centers still wobble slightly when gently shaken. The custard will continue to set as it cools.

Remove the ramekins from the water bath using tongs and let cool to room temperature, about 30 minutes. Cover with plastic wrap and refrigerate for at least 4 hours or overnight.

Just before serving, blot any condensation from the custard surfaces with a paper towel. Sprinkle 1-2 teaspoons of superfine sugar evenly over each custard.

Using a kitchen torch held 3-4 inches away, caramelize the sugar in a circular motion until it bubbles and turns deep amber. Let the sugar harden for 1-2 minutes before serving.