For a delicious cheesy version, beat in 100g/4oz coarsely grated mature cheddar in place of the parsley.
Melt the butter in a large frying pan and
cook the onions and sugar together for
20-30 mins, stirring from time to time,
until very soft and dark golden.
Meanwhile, boil or steam the carrots
for 15-20 mins until very tender. Drain
well and return to the pan. Add the
caramelised onions and using a hand
blender, whizz to make a smooth purée.
Stir in the parsley and serve.