Preheat the oven to 170–180°C.
In a hot sauté pan or frying pan with a drizzle of oil, caramelize the cheeks, seasoning them, until browned all over, and remove to a plate. Add the vegetables and herbs to the pan and cook on a medium heat until really soft – they will deglaze the meat cooking juices. Add the red wine and reduce by almost three-quarters. Add the chicken stock and bring to the boil, then put the cheeks back into the pan – they should be swimming in the liquid. Turn off the heat, cover with foil and cook in the oven for 40–45 minutes, until the cheeks are very soft.
Remove the cheeks to a tray or plate and leave to cool to room temperature (if they are still hot, they will break up when you touch them).
While the cheeks are cooling, pass their cooking liquid through a sieve – press the vegetables down in the sieve with the back of a spoon, then discard. Ladle off as much of the fat that has risen to the surface as possible. Return to the heat and reduce until you have a gravy-like consistency. Keep warm.
Combine the salad leaves and red onion together so they are ready to dress at the last minute.
Coat the cheeks first with the flour, then with the whisked egg, then with the panko crumbs. Heat some oil in a high-sided pan or sauté pan on a medium heat and, when hot, shallow-fry the pig’s cheeks until golden brown. Remove, and drain on kitchen paper.
When you are ready to serve, make a dressing for the salad by mixing the vinegar, olive oil, salt and pepper together. Drizzle the dressing over the salad and serve with the pig’s cheeks, with the gravy in a little ramekin or bowl on the side for dipping.