1-2 tbsp icing sugar
1-2 tbsp cornflour
A little vegetable oil for oiling the tin and knife
1 small, raw, peeled beetroot
25g gelatine powder (about 2 sachets, but check the packet)
500g granulated sugar
2 egg whites
Sift the icing sugar and cornflour together into a small bowl.
Rub a shallow cake tin of about 20x20cm with a few drops of vegetable oil and shake a little of the icing sugar mixture around the tin to coat the base and sides.
Grate the beetroot into a small bowl and pour over 125ml of nearly boiling water and leave to infuse for 30 seconds. Strain the pink, nearly boiling water into a bowl and sprinkle the gelatine on top. Stir until all of the gelatine has dissolved.
Put the sugar into a medium-sized saucepan with 250ml of water. Warm over a low heat, stirring until all of the sugar has dissolved, then place a sugar thermometer in the pan and raise the heat, allowing the mixture to boil fiercely without stirring until the thermometer reads 122°C. Remove from the heat and pour the beetroot/gelatine mixture into the hot sugar syrup, stirring until everything is well blended.
Pour the egg whites into the large bowl of a mixer and beat until stiff. With the mixer going at a low speed, slowly pour in the sugar mixture in a steady, gentle trickle. After you’ve added all of the syrup, leave the machine to carry on beating until the mixture turns really thick and bulky but is still pourable – when you lift up the beater, it should leave a ribbon trail of the mixture on the surface which takes a few seconds to sink back down into the mix.
Pour the marshmallow into the prepared tin. Leave to set in a cool place (do not refrigerate) for an hour or two.
Dust a chopping board with the rest of the cornflour and icing sugar mixture. Coat a knife with a little oil. Carefully ease the marshmallow out of the tin onto the board, helping it out where necessary with the knife. Make sure all of the surfaces of the marshmallow are entirely dusted with the icing sugar mixture. Cut the marshmallows into squares, oiling and dusting the knife as needed. Store in an airtight tin lined with baking parchment.