The first step is to grease a 20cm square cake tin with vegetable oil. This will prevent the Kendal Mint Cake from sticking to the tin and make it easier to remove later.

In a large saucepan, combine the granulated sugar, water, and glucose syrup. Place the saucepan over low heat and stir the mixture until the sugar has completely dissolved.

Increase the heat to medium-high and insert a candy thermometer into the mixture. Heat the mixture, stirring occasionally, until it reaches a temperature of 150°C (300°F).

Once the mixture reaches the desired temperature, remove the saucepan from the heat and stir in the peppermint extract. Stir the mixture vigorously to ensure that the peppermint extract is evenly distributed throughout the mixture.

Carefully pour the mixture into the greased cake tin. Use a spatula to smooth the surface of the mixture and ensure that it's evenly distributed in the tin.

Allow the Kendal Mint Cake to cool and set for at least 30 minutes. Once it has set, remove it from the tin and cut it into small squares or rectangles. Wrap the squares in greaseproof paper to prevent them from sticking together.