Bring 1 2/3 cups cream to a boil in a saucepan over medium heat. Remove from the heat, add the cardamom, cover and let steep 30 minutes.
Preheat the oven to 325 degrees F. Bring a small pot or kettle of water to a boil. Place a folded damp kitchen towel in a 2-quart baking dish; arrange 8 espresso cups in the dish (the towel will keep the cups from moving).
Whisk the egg yolks and salt in a bowl. Return the cream to medium heat, add the sugar and bring to a boil, stirring to dissolve the sugar. Strain the cream into the egg yolks, whisking constantly. Stir in the espresso and vanilla until combined. Transfer to a liquid measuring cup, then divide among the espresso cups.
Place the baking dish in the oven and pour boiling water into the dish until it reaches halfway up the outside of the espresso cups. Cover the dish tightly with foil and bake until the custard sets around the edges but still jiggles in the center, 35 to 45 minutes.
Let the custards cool in the water bath, about 10 minutes, then transfer to a rack to cool completely, about 30 minutes. Cover each cup with parchment paper (to absorb condensation), and then plastic wrap. Refrigerate until set, at least 2 hours.
Whip the remaining 1/2 cup cream and the confectioners' sugar with a mixer until soft peaks form. Top each pot de creme with a dollop of whipped cream and sprinkle with pistachios.
Photograph by Kana Okada
Courtesy of Food Network Magazine