Slice away a piece of each of the bell peppers. Finely chop and put aside to be used as a garnish.
Heat the olive oil in a large pan and fry the chopped onion.
Once the onion becomes transparent, add the garlic to the pan.
Finely slice the rest of the bell peppers and add to the onion.
Add the stock. Bring to the boil, reduce the heat and simmer for 10 minutes.
Finely blend the soup using a hand blender.
Divide the soup over 4 bowls and garnish with the reserved chopped bell peppers, and chopped parsley if you wish.