1. Whisk the butter and sugar together in a bowl until pale and fluffy. Gradually beat in the egg.
2. Sift the flour and ginger into the mixture and work in with a fork until a fairly firm dough is obtained.
3. Roll the dough into small balls about the side of a walnut and put them on buttered baking sheets, spaced apart.
4. Bake in the oven at 150°C (300f) mark 2 for 40 - 45 minutes until crisp, well risen, hollow and very lightly browned.