Place sugar and water in a small saucepan and bring to the boil, stirring until dissolved. Once it comes to the boil, don’t stir. When it becomes a caramel colour (about 7 minutes), add rosemary, garlic and chilli and gently stir. The caramel will burn if you’re not careful. After 10 seconds, add vinegar, water and seasonings and simmer for a further 2 minutes.