Heat the oil in a saucepan, and add the garlic and onion. Cook over a medium heat for 5 minutes, stirring regularly, until soft.
Add the passata, vegetable stock and thyme, and mix well. Bring to a gentle simmer, and cook for another 5 minutes.
While the soup is bubbling, add the pine nuts and fresh basil to a mini food processor, and blitz for a few seconds until a coarse crumb is formed. Set aside.
If desired, blitz the soup with an immersion blender until smooth.
Season the soup with plenty of black pepper (you might not need salt unless you used low-sodium stock). Remove from the heat, and add the sour cream (or Greek yogurt). Mix well, and serve warm, topped with the basil and pine nut crumb.