For the Pots de Crème:

Bring 1 2/3 cups of cream to a boil in a 1-quart saucepan over medium heat. Turn off the heat, add the cardamom seeds, cover the saucepan, and let the mixture steep for 30 minutes.

Position a rack in the center of the oven and preheat the oven to 325°F. Place the ramekins in a 2-quart baking dish.

Whisk the egg yolks in a large mixing bowl to break them up. Add the brown sugar and salt and whisk to blend smoothly.

Uncover the saucepan and bring the cream to a boil over medium heat. Strain the cream into the egg yolk mixture, whisking constantly. Add the vanilla and blend thoroughly. Pour the mixture into a 2-cup liquid measuring cup and divide it evenly among the ramekins, filling each almost to the top.

Carefully pour the boiling water into the baking dish until it reaches partway up the sides of the ramekins. Cover the baking dish tightly with aluminum foil. Bake for 28 to 30 minutes, until the custards are set around the edges but slightly soft in the center.

Remove the baking dish from the oven. Remove the ramekins from the water bath and cool on a rack. Cover loosely with waxed paper and then tightly wrap with plastic wrap and chill at least 2 hours.

For the Garnish:

Whip the remaining ¼ cup of cream in the bowl of an electric stand mixer with the wire whip attachment or in a medium mixing bowl using a hand-held mixer on medium speed until frothy. Add the confectioners sugar and continue whipping the cream until it holds soft peaks.

Fit a 10- or 12-inch pastry bag with a large open star tip and fill the bag partway with the whipped cream. Pipe a rosette or a star in the center of each custard, or add a dollop of whipped cream on top.