Over medium-high heat, combine 1/2 cup of water, sugar, corn syrup and salt. Cover and allow to cook for 3-4 minutes. Uncover, and attach a thermometer to the pan and continue to cook until it reaches 240F, (7-8mins). Remove from heat immediately after.
Mixer on low speed, slowly pour the sugar syrup into gelatine mixer. Change to high speed, continue to whip for 12-15 minutes. The mixture should be warm and very thick.
Add sugar and cornstarch mixture to pan and shift around until it's completely covered. Return rest of mixture to bowl for later use.
Pour Mixture into the pan using a lightly oiled spatula to spread evenly. Dust the top with remaining sugar and cornstarch mixture.