Preheat the oven to 140⁰C (275⁰F) and lightly grease a square (21 x 21 cm) 7 x 7 inch cake tin.
In a saucepan, melt together the butter, brown sugar, black treacle and golden syrup on a medium-low heat.
Stir all the dry ingredients in a large mixing bowl.
When the syrup mixture is ready, tip it into the dry ingredients.
Use a wooden spoon to beat the wet ingredients into the dry.
Incorporate the eggs bit-by-bit to avoid curdling the mixture.
Slacken the mixture with the milk and pour it into the cake tin.
Cook for 1 hour and 30 minutes and cool it in the tin.
Once cool, keep the parkin in an air-tight cake tin or tub for at least three days before cutting into squares.
