Line a 23cm x 33cm baking tray with baking parchment or a silicone baking mat; lightly grease if using parchment.
In a medium, heavy-based saucepan, combine the caster sugar, water, golden syrup and fresh lemon juice. Stir over a medium heat until the sugar dissolves, then stop stirring.
Add the hulled and chopped strawberries. Bring to the boil over a medium-high heat and clip in a sugar thermometer, ensuring it doesn’t touch the base of the pan.
Cook without stirring until the mixture reaches 118°C, about 15–20 minutes, watching the thermometer closely.
Remove from the heat and immediately pour onto the prepared tray, spreading to a thickness of 6–12 mm.
Leave the sweets to set at room temperature for 2–3 hours (or chill for 30–60 minutes), then lift off the parchment and cut into squares using a lightly oiled knife or kitchen scissors.
If you like, lightly dust the pieces with icing sugar to prevent sticking.