Bring a saucepan of water to the boil. Add broccoli and simmer five minutes. Drain and set aside.
Heat the olive oil in a heavy saucepan or casserole. Add the garlic and fry 2 minutes. Add the broccoli, season with salt and pepper and stir well. Cover and cook over very low heat 1 hour, stirring occasionally.
Next, add the vegetable stock. Bring to a boil and simmer 5 minutes. With an immersion blender, blend soup to your desired degree of smoothness.
Stir in Parmesan and lemon juice. Adjust salt and pepper if necessary and serve with extra cheese and fresh bread.