Blacken the whole garlic and the onion
slices on all sides in a large, dry non-stick
frying pan. Remove, cool briefly, then
peel the garlic cloves. Soak the ancho
chilli in boiling water for 15 mins, drain,
then place in a blender with the sugar,
cider vinegar, garlic, onion and some salt
and pepper. Whizz to a smooth sauce.