Add the onions and saute on medium heat until translucent.
Add the garlic and stir for about a minute.
Add the butternut squash and chilli powder. Cook for about a couple of minutes, stirring occasionally, so the squash breaks down further.
Add half the cooked beans and salt to taste. Bring to a boil.
Turn off the heat and, with an immersion blender or in a regular blender, puree the soup until it acquires a rich, creamy texture. (Pureeing half the beans gives the soup its creamy texture while the remaining limas go into the soup whole to contribute a hearty heft.)
Return the saucepan to heat, add the remaining lima beans and season with salt if required.
Warm to a simmer, then turn off the heat and ladle the hot soup into bowls.
Garnish with the diced avocado and enjoy with some bread.