Carrot & parsnip soup

Name: Carrot & parsnip soup
Prep time: 20 min
Cook time: 35 min
Total time: 55 min
Cuisine: European, British
Ingredients: ½ tbsp olive oil; 2 onions finely chopped; 2 celery sticks finely chopped; 2 garlic cloves crushed; ½ small bunch thyme leaves picked; 3 large carrots peeled and roughly chopped; 2 large parsnips peeled and roughly chopped; 1 litre vegetable stock; 100ml double cream; ¼ bunch parsley finely chopped (optional)