Lightly toast the coconut over low heat, tossing it from time to time. Let cool completely.
Add the biscuits to a food processor; process until finely ground.
In a bowl, mix 1 cup of the finely ground biscuits with the toasted coconut, cinnamon and ginger. Pour in the condensed milk and mix well.
Wet your hands in water to prevent sticking, and then scoop a heaped 1/2 tablespoon of the truffle mixture and shape into a ball. Drop the ball in the melted chocolate and rotate to make sure it is fully covered. Remove with a fork and tap off excess chocolate. Transfer to a roasting tray, tightly wrapped with plastic wrap to create a springy base for the truffles to set on--this makes sure the balls don't get a flat base. Repeat until you have 8 to 10 truffles.
Leave to cool until the chocolate sets. Once set, transfer the truffles to a lidded jar.