Mix the cordial and warm water together in a small pan and sprinkle the gelatine over, gently stir and set to one side to allow the gelatine to swell or "bloom".

Place the sugar, syrup and remaining water into a heavy saucepan and bring to the boil.  Simmer until the syrup is at 120C.

Whilst the sugar is heating, line a baking pan (about 30 x 20cm) with oiled cling film (I pour a small dab of oil on to the film and then scrunch it up to coat it).

If needed warm the gelatine gently to fully dissolve add it to the bowl of your stand mixer and mix on a low speed with the whisk to prevent it from setting.

Once the sugar syrup has reached 120C increase the speed of the mixer to maximum and carefully pour the syrup over the gelatine.    Whisk.   The mix will puff up and after 5 - 10 minutes bubble gum like strands form.   Add a few drops of food colouring if desired.

Dollop into the prepared pan and leave at room temperature for 2 hours until set.

Mix the cornflour and icing sugar and liberally dust a board with it, turn the set block of marshmallow out, teasing the cling film from it.     With an oiled serrated knife cut the marshmallow into cubes dusting each freshly cut surface with the cornflour mix as you go.     I found the cutting was the hardest part of the process, the marshmallow is fairly forgiving and robust so you can pull it around a fair bit.