Combine the water and cardamom pods in a medium saucepan and bring to a boil. Turn off the heat, add the tea bags and stir gently. Steep for 10 minutes, then remove the tea bags. Add the sugar and condensed milk and stir with a wooden spoon until all of the sugar is dissolved. Allow to cool.
Remove 1 1/2 cups of the cooled tea mixture from the saucepan and pour this into an ice cube tray. Freeze for at least 4 hours. Strain and refrigerate the remaining tea.
When ready to serve, divide the tea ice cubes between four glasses. Fill the glasses with the chilled tea mixture, leaving a little extra space at the top. Top each glass off with 2 tablespoons of the half-and-half. Serve garnished with a slice of candied ginger, a stalk of lemon grass or a mint sprig, if desired.