Cook in microwave oven at 50% power (medium) for 3 minutes, stirring twice. Cook at 30% power (medium low) for 8-12 minutes, stirring every 2 minutes. Then allow it to cool (it will caramelise and become like a thick sticky fudge).
Peel and mince the ginger.
Beat butter till soft. Stir in the eggs, flour and mix till smooth.
Add the condensed milk and mix till smooth.
Pour the mixture in a greased 1 litre pudding mould. Cover with double layer of aluminium foil. Steam for 1 hour.