Preheat the oven to 150°C/300°F/ gas 2. In a bowl, beat the butter with the sugar until pale and light. Sift in the flour and ground ginger, then whisk to incorporate.
Use a dessertspoon to scoop out amounts sufficient to make walnut-sized balls, rolling them between floured hands. Put these on a non-stick baking sheet and press them down gently into ovals. As they cook they will spread and set as thin biscuits.
Bake for 50–60 minutes, when they will be crisp and golden brown. Use a spatula to remove them to a wire rack to cool. If given the opportunity, they keep for a week in an airtight tin before going soft, but can be crisped back to life with 10 minutes in a low oven.