Heat your oven to 200°C/Fan 180°C/Gas 6. Peel the pears and quarter them. Slice out the cores and chop into small chunks. Scatter into a roasting tin and sprinkle over a pinch of salt and pepper. Pour over 1 tbsp olive oil and toss well to evenly coat. Slide into the oven to roast for 15 mins, till golden.
Meanwhile, peel and crush or finely chop the garlic. Peel the onion and finely chop it. Pick the rosemary leaves and finely chop them. Pour 1 tbsp oil into a pan and bring to a medium heat. Slide in the onion, garlic and rosemary and stir in a pinch of salt and pepper. Fry for 3-4 mins, till softened.
Peel the potatoes and dice them. Slide into the pan and crumble in the stock cube. Pour in 800ml boiling water and stir. Bring to the boil, then reduce to a simmer and cook for 10 mins.
While the potatoes cooks, trim the base off the cabbage. Finely shred the leaves. When the potatoes have had 10 mins, slide the cabbage into the pan and simmer for a further 6-8 mins, till the cabbage leaves are tender.
The pears should be cooked by now. Slide half into the soup, and use a stick blender to whiz into a smooth soup. No stick blender? No problem. Simply transfer the soup into a blender (in batches if necessary) and blitz till smooth.
Ladle the cabbage and pear soup into deep bowls and top with chunks of roasted pear and a generous crack of black pepper.