Heat up oil in a medium-sized pan, over medium heat. Add garlic and onion and cook until soft and fragrant. Add carrot and celery and cook until the vegetables are slightly softer.
Add potatoes, yellow peppers and vegetable broth. Bring to a boil. Lower heat and simmer for 35 to 40 minutes, or until the vegetables are fully cooked and very soft.
Take soup off the heat and blitz (or use a blender). Put the pureed soup in a clean pot.
Heat up the pureed soup and add salt and pepper to season.
Serve on soup bowls with regular croutons (or croutons with parmigiano), and parsley (if desired).