Preheat oven to 170C/340F/Gas 3 to 4. Grease and line a large roasting tin or Pyrex dish with baking paper.

In a large bowl, mix flour, sugar, oats, ground ginger, and chopped preserved ginger.

Melt butter in a saucepan. Add golden syrup and treacle; warm through but do not boil.

Pour the butter mixture into the well of the dry ingredients. Add bicarbonate of soda and sprinkle vinegar over it, letting it fizz.

Gently heat the milk in the saucepan used for the butter mixture until hand hot.

Add the milk to the ginger parkin mixture and mix well to form a loose batter.

Pour the batter into the prepared tin and bake for 1 hour, until it springs back when touched and is dark brown with a sticky surface.

Cool completely in the tin, then cut into slices or chunks.

Store in an airtight tin for 2-3 days before eating for the best flavor, or freeze for later.