Preheat the oven to 160C/325F/Gas 3.
Grease a 20cm/8in square baking tin and line with baking parchment.
Place the butter, sugar and golden syrup into a pan over a medium heat and cook until melted and combined.
Sift the flour, bicarbonate of soda and ground ginger into a bowl and mix well.
Add the melted butter and sugar mixture to the dry ingredients.
Add the egg and beat the mixture to a thick pouring consistency. If the mixture is too stiff, add a little milk to loosen.
Pour the cake mixture into the lined cake tin and bake in the oven for one hour, or until the centre is firm and springy to the touch.
Allow to cool, then cut into squares. (This cake keeps in a tin for 2-3 weeks. The longer you leave it better it tastes.)