Preheat the oven to 140C/120C fan/Gas Mark 1. Grease and line a 20cm x 20cm square cake tin.
In a pan, over a gentle heat, melt the butter, sugar, treacle and golden syrup. Don't allow the mixture to get too hot or bubble. When they have melted together remove from the heat and allow to cool slightly.
In a large mixing bowl sift in the dry ingredients and make a well in the centre. Gradually add the melted butter mixture and fold together. Pour in the beaten eggs and milk and combine together.
Pour into your baking tin. Bake for 1 1/2 hours, however keep an eye on it as parkin can easily become dry and over baked.
Remove from the oven and leave in the tin for 20 minutes. Tip onto a cake rack and leave to cool completely.
Store the parkin in a cake tin and wrapped in greaseproof paper. You must keep it in a tin for a minimum of 1 day and up to a week before you cut it. Leaving it to develop will give it a moist and sticky texture, as well as making the flavour richer and deeper.