May I suggest...
Preheat the oven to 150C/300F/Gas 2 and line a small, deep baking tray with parchment paper. Combine the oatmeal, flour and ginger in a large mixing bowl.
Melt the sugar, butter, syrup and treacle in a bowl in the microwave or in a saucepan over a low heat. Pour the melted ingredients into the flour with the eggs and milk and stir well.
Pour the mixture into the prepared baking tray.
Bake for 45 minutes until golden brown, but still soft and sticky on top. Reduce the oven to 130C/250F/Gas 1 and bake for a further 30 minutes until firm to the touch.
Allow to cool, before tightly wrapping in cling film. Store for at least three to five days to mature.