Onions, pumpkin, ginger
Chop the pumpkin into large chunks, removing the seeds for roasting.
Slowly cook the chunks of pumpkin with minimum water. When the pumpkin is soft, blend into a puree: the thicker it is, the less space it will take in the freezer.
Gently fry onions and finely chopped ginger root. Other flavours can be added: cumin, grated nutmeg, ...
Mix pumpkin puree in with the onions. Add enough water until the soup is as thick as you want.
I freeze "bricks" (the concentrated paste freezes well in plastic containers. You then empty the frozen bricks, and mould some more bricks). When you want a quick soup weeks later, pour boiling water on a brick - in a few minutes, you will have soup for four.