1. Heat oil in large pot over medium heat. Add onion and celery and cook until softened, about 5 minutes. Add garlic, parsley, thyme, salt, and pepper and stir for about 30 seconds until combined.
2. Increase heat to high and add peas, chicken broth, and water. Bring to a simmer for about 3 minutes. Turn off heat.
3. Ladle soup into blender and puree until smooth consistency is reached (be extra careful with hot liquid and steam). Add Parmesan cheese and butter and puree for another 5 seconds to combine. Serve warm.