Lightly grease the bottom and sides of a 23x33cm (9x13in) tin and line the base with non-stick baking (parchment) paper. Heat a frying pan over high heat, then add in the coconut. Stir regularly to toast the coconut for 3 to 4 minutes or until golden. Place enough coconut to cover the base of the tin evenly. Store the remaining coconut in an air-tight container for later.
In a medium heavy-based saucepan; place in the glucose syrup, sugar, salt and 1/2 cup of water. Place the pan over medium heat and stir slowly just until the sugar dissolves, then stop stirring. Allow the sugar mixture to come to a boil.
Meanwhile, bloom the gelatine - Pour 1/2 cup of cold water into the bowl of a stand mixer and sprinkle the gelatine on top. Give it a quick mix and leave it to bloom whilst finishing the sugar mixture.
Once the mixture comes to a boil, cover the saucepan for a minute. Doing this will help get rid of any sugar crystals stuck on the side of the pan. Uncover the pan and boil until it the temperature is between 115 - 118°C (239 - 244°F). Remove the pan from the heat.
Place the stand mixer at low speed. Carefully pour in the sugar mixture slowly into the gelatine with the mixer running. Once the sugar mixture is all in, gradually increase the speed of the mixture to high. Whip the marshmallow mixture for approximately 10 to 15 minutes or until thick and glossy. Pour in vanilla extract and whip on high for another 30 seconds or until combined.
Pour the marshmallow onto the prepared tin over the toasted coconut with a spatula. Spread the mixture in the pan evenly, then sprinkle some toasted coconut on top. Leave the uncovered marshmallow to set at room temperature until firm. This can take up to 5 to 6 hours.
Once set, use a thin blunt knife or spatula to pry the marshmallows from the sides of the tin. Pull the marshmallow out and slice them into desired pieces. Place the remaining toasted coconut into the same baking tin and use it to coat all sides of each slice.