Mix together your baking powder and flour, then rub in the butter until the mixture has the consistency of breadcrumbs (it helps if you keep the butter cold and grate it into the flour).
Mix in your ground ginger, sugar and syrup, then add milk, a little at a time, and combine your mixture into a stiff dough.
Line a loaf tin with greased baking paper, then put the dough in the tin. Sprinkle with a little demerara sugar (or whatever type comes to hand).
Bake until brown and firm – around an hour. To test whether it’s done, insert a metal skewer if you have one. If it comes away from the cake clean, it’s done.
Cool on a rack. Serve with a thick spread of butter.