Preheat oven to 325°F (165°C). Spread pistachios on a small baking sheet and toast for 8-10 minutes until fragrant, shaking halfway through. Let cool slightly, then coarsely chop.

In a medium saucepan, combine heavy cream, milk, and chopped pistachios. Heat over medium heat until small bubbles form around the edges, about 5 minutes. Remove from heat, cover, and steep for 30 minutes to infuse the pistachio flavor.

Strain the cream mixture through a fine-mesh sieve into a clean bowl, pressing on the pistachios to extract maximum flavor. Discard solids. Rinse the saucepan and return the strained cream to it, keeping it warm over low heat.

In a medium bowl, whisk together egg yolks, 1/3 cup granulated sugar, vanilla extract, and salt until smooth and pale, about 1 minute. Slowly pour the warm cream into the yolk mixture while whisking constantly to temper the eggs.

Strain the entire custard mixture through a fine-mesh sieve into a large measuring cup or pitcher for easy pouring. Divide evenly among six 6-ounce ramekins.

Place ramekins in a large roasting pan and carefully pour hot water into the pan until it reaches halfway up the sides of the ramekins. Cover the entire pan loosely with aluminum foil.

Bake for 35-40 minutes until the custards are set around the edges but still jiggle slightly in the center when gently shaken. The internal temperature should reach 170°F.

Remove ramekins from the water bath and let cool to room temperature on a wire rack, about 30 minutes. Cover each with plastic wrap and refrigerate for at least 4 hours or up to 2 days.

Just before serving, pat the surface of each custard dry with a paper towel. Sprinkle 1 tablespoon superfine sugar evenly over each custard, tilting to coat completely.

Using a kitchen torch, caramelize the sugar in a circular motion, holding the flame 2-3 inches from the surface until golden brown and bubbling. Let stand for 2-3 minutes to allow the sugar to harden before serving.