Icing sugar, 1 tablespoon
Cornflour, 1 tablespoon
Vegetable oil for oiling tin and knife
Gelatine powder, 25g
Red food colouring 2-3 drops (optional)
2 Free-range egg whites,Granulated sugar 500g
1. Sift the icing sugar and cornflour together into a small bowl. Rub the tin lightly with just a few drops of oil and shake a little of the icing sugar mix around the tin to coat the base and sides. Set the tin to one side.
2. Bring the kettle almost to the boil, then measure out 125ml water. Pour it into the second small bowl and sprinkle the gelatine on top. Stir with the wooden spoon until the gelatine has all dissolved. If you want the marshmallows to be tinted the traditional pale pink, add the red food colouring to the gelatine and stir again. Leave the dissolved gelatine to stand near the hob.
3. Stand the food mixer on the work surface near the hob. Put the egg whites into the bowl of the mixer.
4. Put the granulated sugar in to the medium saucepan and add 250ml water. Turn the hob on low and stir with a wooden spoon until the sugar has completley dissolved and you can't see any grains left if you carefully tilt the pan. Now stop stiring. Rinse the sugar thermometer under the hot tap for a few seconds so it doesn't get too much of a shock, then stand it in the pan. Raise the heat so the syrup comes to the boil. Meanwhile, switch on the mixer and whisk the egg whites until they're completly stiff. Stand jug with a little hot water in it near the hob.
5. The sugar needs to boil fiercely until it gets to 122C - the hard-ball stage. Watch the thermometer carefully, especially in the later stages of the sugar boiling. As the sugar gets to 122 C, immeadiatly turn off the hob. Using oven gloves or a thick cloth to protect your fingers, take out the sugar thermometer and put it in the jug of water to cool down.
6. Pour the dissolved gelatine into the pan of syrup, stirring all the time with a wooden spoon. The syrup will bubble up a little, although not dangerously so. Stir until the mixture is well blended.
7. Switch the food mixer on low so that the egg whites carry on whisking. Very carefully pour the syrup on to the beating egg whites in a steady, gentle trickle - avoid pouring it on to the beaters or it will splash. You'll see the mixture turn creamy. After you've poured in all the syrup, leave the machine to carry on beating until the mixture turns really thick and bulky but is still pourable. If you lift up the beaters, a ribbon of marshmallow should remain on the surface for a few seconds before sinking back down in to the mix.
8. Pour the marshmallow into the prepared tin. Leave it to set in a cool place, though not the fridge - this will probably take an hour or two. You won't want to wait that long, obviously, but try and be patient.
9. Dust the chopping board with the rest of the cornflour and icing sugar mixture. Coat the butter knife in a little oil. Carefully ease the mashmallow out of the tin on to the board, helping it our where necessary with the butter knife. Make sure the surfaces of the marshmallow are entirely dusted with the icing sugar mixture - sift over extra icing sugar and cornflour, if necessary. Cut the marshmallow into squares, oiling and dusting the knife as it needs it (probably between every cut).
This is a great recipe from the Tv Show River Cottage: