Preheat the oven to 190℃/170℃ fan/375℉/gas mark 5. Line two baking sheets with baking parchment.
Gently heat the golden syrup, treacle, butter, oil, milk, caster sugar and brown sugar in a large pan until melted.
Remove from the heat and whisk in the baking powder, bicarbonate of soda, ground ginger and cinnamon; the mixture will foam up slightly.
Add the plain flour and stir to form a soft dough.
Roll the dough into 16 balls and place them well spaced apart on the baking sheets. The dough is soft but you should be able to shape it into rough balls.
Bake the cookies for 10-15 minutes until lightly browned around the edges. Bake for the shorter amount of time if you prefer really soft cookies, and the longer time if you prefer them more crisp. They will still be very soft when baked, but will firm up a lot as they cool.
Leave to cool on the tray for a few minutes, then carefully transfer them to a wire rack to cool completely.