Combine the caster sugar, unsalted butter, Lyle's Golden Syrup, water, and a pinch of salt in a saucepan.

Place the saucepan over low heat and stir continuously until the sugar has dissolved and the ingredients are combined.

Once the sugar has completely dissolved, increase the heat to medium and bring the mixture to a gentle boil. Stir occasionally.

Allow the mixture to boil without stirring until it reaches the hard crack stage - around 140°C on a sugar thermometer. If you don't have a thermometer, you can test the toffee by dropping a small amount into a bowl of cold water - it should harden immediately and become brittle.

Once the mixture is ready, remove the saucepan from the heat and carefully pour the hot toffee mixture onto the greased baking tray or dish. Spread it out evenly.

Allow the toffee to cool and set completely at room temperature.

Once the toffee has cooled and hardened, cut it with a knife or break it into pieces with a toffee hammer.