The basic toffee recipe involves heating the mixture to either the ‘soft crack’ stage (a temperature of 132-143C/270-290F) or ‘hard crack’ stage (a temperature of 149-154C/300-310F), depending on whether you want to make soft or hard toffee.
When melting the sugar and butter, use a deep-sided pan because the mixture can more than double in volume during preparation. Spread the toffee mixture onto a silicone baking sheet – these can be easily peeled from the cooled, hardened toffee. If you want toffees of uniform shape, score the slab of toffee while it’s cooling to make it easier to break apart when hardened. Otherwise, break the toffee with a toffee hammer once it’s cooled.