Soak the beans overnight.
To make the soup, use a large non-stick pot, warm the olive oil over low heat.
Stir in the onions and birdseye chilis. Cover and cook on low heat until the onions are translucent but not brown.
Add minced garlic and cook for further 10 minutes.
Tip in drained, soaked beans (discard the soaking water) and stir into the soup base.
Add stock and bring to simmer (not boil).
Simmer on low for about 1 hour until the beans are cooked through.
With a ladle, remove about half of the beans from the soup.
Either leave the birdseye chilis in the pot or discard them. The soup will be more spicy if you leave them in.
Using a stick blender, blend the contents of the pot until smooth.
Add back the reserved beans and onions.
Heat through. Stir in coriander just before serving.
Serve in bowls with additional garnish as desired.