Pumpkin, lentil and ginger soup

This is delicious.  The ginger gives it a zing! 

1/2 cup red lentils

1 kg jap or butternut pumpkin cut into chunks

1 tbs ginger, grated

1 tbs orange zest

4 cups vegetable stock

1/2 cup buttermilk

1/4 cup coriander, chopped

Rinse the lentils and place in pot with the pumpkin, ginger and orange zest.  Add the stock and bring to boil.  Reduce to simmer and cook for 30 mins.  Remove from heat.  Blend with stick blender.  Stir through buttermilk and top with chopped coriander.