Line a 8 x 8-inch (20 x 20 cm) square baking pan with parchment.

Add the sugar and corn syrup to a saucepan over medium heat until melted, stir to mix. Cook until a candy thermometer reads 295°F/146°C (the hard crack stage, which will take about 15-20 minutes) until golden brown without stirring. Turn off heat and when bubbles disperse whisk in the baking soda until the color is uniformly golden. Pour into prepared pan and allow to set for 2 hours.

If you are coating the toffee in chocolate. Break up the chocolate and add to a microwave-safe bowl. Microwave on high for 30 seconds then stir. Continue this until melted. After breaking up the toffee, dip the pieces in the chocolate and place on a plate or parchment/baking paper until set.

This will last for 1-2 weeks in a well sealed container at room temperature.