Put the butter, syrup and sugar in a saucepan and heat gently, stirring until the butter has melted and the sugar dissolved. Remove the pan from the heat then stir in the bicarbonate of soda, ground and chopped ginger. Add the flour and oats and mix well.
Spoon heaped teaspoons of the mixture on to 3 lightly greased baking sheets, leaving a little space between for the biscuits to spread during cooking.
Cook one baking sheet at a time in the centre of a preheated oven, 180°C (350°F), Gas Mark 4, for 8–10 minutes until the biscuits are craggy and golden. Leave to harden for 1–2 minutes then loosen and transfer to a wire rack to cool. Store in an airtight tin for up to 3 days.