Peel and finely slice the red onions.
Heat the butter and oil in a small saucepan over a medium heat and ad the red onions.
Cover with a lid and cook for 8-10 minutes until softened and starting to colour.
Remove the lid and turn the heat up high.
After a minute add the balsamic vinegar and cook, stirring all the time, until it evaporates.
Remove the onions from the heat replace the lid and set aside.
Place the cousous in a large, heatproof bowl and add the grated zest of the lemon.
Add 1 ½ cups of boiling water, cover with clingfilm and leave to absorb the water.
Slice the liver into 1cm/ 1/2in thick slices, season with salt and pepper, and sprinkle with the flour, making sure the meat is coated all over.
Fry the liver in batches over a medium/high heat in a non-stick pan for 40 seconds – 1 minute on each side, remove and keep warm in a medium heated oven.
Once the liver is fried and the couscous has absorbed the water, you are ready to serve.
Roughly chop the parsley, add half of it to the bowl of couscous and fluff it up with a fork, mixing well.
Serve the couscous on separate plates topped with the red onions and liver. Garnish with the remaining parsley and a wedge of lemon.