Beat the sugar and egg with an electric whisk for 1-2 mins until smooth.
Add the peanut butter and whisk again until combined.
Cover with clingfilm and chill for 30 mins.
Preheat the oven to gas 4, 180°C, fan 160°C and line 2 baking trays with nonstick baking paper.
Using a dessertspoon, scoop out 10 balls of dough, about 45g each.
Flatten the bases a little and arrange on the baking trays at least 6cm apart.
Bake for 12-15 mins until golden at the edges.
Leave to cool on the trays for 15 mins, then transfer to a wire rack to cool completely.
The cookies will keep in an airtight container for up to 3 days.
