To a medium-sized pot, heat olive oil over medium heat. Once hot, add onion and celery and saute for 7-8 minutes.
Next, add the potatoes and garlic and continue cooking for 2-3 minutes, or until the garlic is fragrant and you can smell it.
Add vegetable broth, salt, black pepper, and stir. Bring to a boil and simmer on medium heat for 10 minutes.
Add broccoli and continue cooking for 7-10 more minutes. Then, add frozen peas and simmer for 3 minutes. When all of the vegetables are soft, remove from the heat and add the parsley or any fresh herbs of choice.
Using an immersion blender, blend the soup until creamy and smooth. (If are using a standard blender it's important to let the soup cool a bit before transferring it. Don't fill the jar more than halfway and make sure that you leave the hole in the lid open so that heat can escape).
Add this point, you can taste and adjust the seasoning, and the thickens of the soup if needed. If it's too thick, add more vegetable broth, one cup at a time, until you reach the desired consistency.
Serve with lemon juice if desired!