Wash broccoli and potatoes thoroughly and cut them into small pieces.
Finely chop the onion.
Heat olive oil in a pot and sauté the onion.
Add potatoes and broccoli and stir-fry together.
When the vegetables are cooked, add water or vegetable broth and bring to a boil.
Once the vegetables are tender, blend until smooth.
Add milk and season with salt and pepper.
Bring it to a boil one more time to finish.