Toffee apples: Crisp, juicy apples in a crunchy, super-sweet coating

Steps
1. Wash 6 British eating apples and dry with kitchen paper.
2. Insert a lolly stick through each core. Grease the baking paper with butter and put on a baking tray. Put a bowl of cold water in the fridge.
3. Put 450g demerara sugar in a pan with 50g unsalted butter, 2tsp cider vinegar and 1tbsp golden syrup. Add 150ml cold water and heat, stirring gently, until the sugar has completely dissolved.
4. Bring to the boil, then boil for 10 minutes until it turns to toffee. To test if it's ready, drop a small piece into the bowl of cold water. If it goes hard immediately, it's ready.
5. Remove from the heat and dip the apples in, swirling them around gently until coated. Put on the greased paper and leave to set.