Cut the lemongrass and puree in a blender or food processor with a little water to make a paste.
In a skillet or a wok heat oil or butter.
Add the leeks and saute for about a minute.Add the ginger,garlic and lemongrass.
Saute for another minute or two.
Add the cumin and coriander.Saute until fragrant.
Add the cubed butternut squash.Mix well.
Add coconut milk and salt and bring to a boil.
Reduce the heat, cover and cook until the squash has cooked but still holds it shape (about 10 minutes).
Add a little water if too thick.
Serve hot on a bed of rice.
Enjoy.