Preheat oven to 180C.
Beat together the Demerara sugar, eggs and jam.
Sift together the flour, cocoa powder, baking powder, salt
Fold the dry ingredients into the egg mixture, alternating with the milk.
Mix together the bicarb and vinegar, then mix into the batter.
Pour the batter into a baking dish then bake for about 20 to 30 minutes or until golden brown and risen.
Make the sauce by placing all the ingredients into a pot and bringing to the boil.
Pour the sauce onto the cooked pudding as soon as it comes out of the oven.
Serve with custard or with a scoop of vanilla ice cream.