Place the sugar, water and powdered gelatine in a small saucepan and heat to 123°C on a sugar thermometer. Add the agar and bring the heat up to 125°C. Whisk in the sesame paste.
Dust a small tray with the cornflour and pour in the marshmallow mixture. Allow to cool and cut into matchbox-size pieces.
Skewer each sesame marshmallow and toast over charcoal, as you would by the campfire.