25 gmpowdered gelatine185 ml(¾ cup) lemon juice½lemon, finely grated rind only500 gmcaster sugar1 tbspliquid glucose2eggwhitesFor dusting:snow sugar (see note)Lemon sherbet75 gmcitric acid (see note)95 gmpure icing sugar1 tbspbicarbonate of soda, finely sieved1lemon, finely grated rind only
Combine gelatine, lemon juice and rind in a small bowl and stand until lemon juice is absorbed (1-2 minutes). Fill a bowl with boiling water and place bowl of gelatine mixture on top and stand until gelatine has dissolved (1-2 minutes). Keep warm.
Combine sugar, glucose and 200ml water in a saucepan. Bring to the boil, stirring to dissolve sugar, then brush down sides of pan using a wet, clean pastry brush and cook over medium heat until syrup reaches 125C on a sugar thermometer (5-10 minutes).
Meanwhile, whisk eggwhites using an electric mixer on medium speed until soft peaks form. Increase speed to high and whisk to firm peaks. With motor running and mixer speed on medium, slowly and simultaneously add syrup and gelatine mixture in a thin stream. Whisk until mixture cools to blood temperature. Spoon into a baking paper-lined 20cm-square cake tin, smooth top using a wet palette knife and refrigerate until firm (1-2 hours). Cut into cubes, roll in snow sugar and refrigerate until required.
For lemon sherbet, sift ingredients through a fine sieve into a dry bowl (sherbet must remain dry to retain fizz effect). It will keep refrigerated in a dry airtight container for 1 week.
Serve marshmallows dusted heavily in lemon sherbet and eat immediately.
Note Snow sugar is a mixture of icing sugar and vegetable fats, resulting in an icing sugar that can be used to dust slightly moist cakes without dissolving as quickly as ordinary icing sugar. It is available from select delicatessens. Substitute with icing sugar. Citric acid is available from the baking section of major supermarkets. Make sure all ingredients for lemon sherbet stay completely dry otherwise you wil lose the fizz effect.