Heat oven to 120C (100C fan)/250F/gas low. Line two trays with greaseproof paper.
Whisk egg whites & cream of tartar until frothy. Add half the sugar, whisk until thick, then add the rest & beat until stiff peaks form.
Mix in cornflour slowly, then spoon onto trays—leave space between as they'll spread!
Bake 1.5–2 hrs until light, crisp & easy to lift off the paper.
Cool completely & store in an airtight container for up to 3 days.
