Pre-heat your oven to 160C Fan/180C/300F/Gas Mark 2 and line a 12" x 9" traybake tin with baking paper
In a pan on a low heat, melt the together the butter, light brown sugar, black treacle and golden syrup
In a large bowl mix together the oats, plain flour, baking powder, ground ginger, mixed spice, nutmeg and salt
Pour the warm treacle mixture into the bowl and combine the ingredients
In a small bowl beat the eggs with the milk. Add them bit by bit to the rest of the mixture, mixing in well each time
Pour the mixture into the lined tin and bake for 35 minutes. It must be firm on top all the way to the centre
Allow to cool, then cut into squares. You can eat it immediately or for a stickier cake, put it into an airtight container and leave for 3 - 5 days
Notes
Mixed spice is a British spice blend containing Cinnamon, Coriander Seed, Nutmeg, Clove, Pimento, Ginger. If you can't get hold of it, use a Pumpkin Spice mix instead