Place white chocolate in a medium heatproof bowl. In a small pan over medium heat, bring heavy cream just to a simmer. Pour the cream over the chocolate; stir in chopped crystallized ginger. Chill until just firm, about 2 hours. In a bowl, whisk sifted confectioners' sugar and ground cardamom. Using a 1/2-oz. ice cream scoop or a tablespoon measure scoop up the ganache and roll into balls. Roll in the cardamom sugar. Place on a rimmed baking sheet lined with parchment or wax paper and chill until firm, about 30 minutes.