Work quickly to make these marshmallow strings in order that the mixture doesn’t set in the piping bag. Getting them twisted takes a bit of practice, too, but they are great fun!
Mix together the icing sugar and cornflour, reserve one third of the mixture, then sprinkle the remainder evenly over the 2 lined baking trays and set aside.
Soak the gelatine leaves in a large, flat dish, such as a baking dish, for 5 minutes, ensuring the leaves are fully submerged.
While the gelatine is soaking, place the glucose in a small pan with 150ml of water. Reserve 1 tablespoon of the caster sugar, and place the remainder in the pan. Dissolve the sugar over a medium heat, then increase the heat and boil until the syrup reaches 120°C/248°F on a sugar thermometer. Remove the syrup from the heat.
Shake the excess water from the gelatine leaves and stir them into the pan with the syrup until dissolved. Set aside.
Place the egg white, salt and the reserved 1 tablespoon of sugar in the bowl of a stand mixer fitted with the whisk. Mix on medium speed until fluffy, then increase the speed and whisk to soft peaks.
With the whisk running on a high speed, slowly add the syrup to the eggs, whisking for about 10 minutes, until the outside of the bowl is at room temperature. Whisk in the rose water to combine.
Very quickly divide the mixture equally into 2 bowls. Add a little pink food colouring to 1 of the bowls and green to the other and mix well to give even pastel shades.
Transfer each mixture to a piping bag and pipe long lengths of each colour on the baking sheets (it doesn’t really matter how many you pipe, but keep each colour equal in number and length), making sure the lengths don’t touch each other. Sprinkle over half the reserved cornflour and icing sugar mixture.
Leave the marshmallows to set for 1 hour, then dust again with the remaining cornflour and icing sugar mixture. Take 1 length of each colour and twist them together in a long rope. Repeat with all the lengths. You can leave them long, or cut them into shorter ‘flumps’. They will store in an airtight container for up to 3 days.