2 teaspoons unsalted butter, chilled and cut into small pieces
1/8 cup freshly chopped rosemary
Place the cream, vanilla bean, and cardamom pod in a heavy saucepan and bring to a boil. Reduce the heat and simmer for 5 minutes, stirring occasionally. Set aside.
Whisk the egg yolks and 2 tablespoons of the sugar in the top of a double boiler over simmering water until pale and thick. Do not overcook.
Remove the vanilla bean and the cardamom pods from the cream. Add the cream to the eggs in the double boiler, whisking constantly. Cook slowly, stirring occasionally, until the mixture thickens and coats the back of a spoon, approximately 10 minutes.
Remove from heat and whisk in the butter and rosemary. Pour the custard mixture into a porcelain dish and chill thoroughly.
Just before serving, sprinkle the custard with remaining sugar and caramelize it with a kitchen torch. Fire quickly and evenly until the sugar is cooked but not burned. Put the creme brulee into the freezer for about 30 seconds and then serve immediately.