Place the beef cheeks in a large bowl add the vegetables, herbs and peppercorns; pour over the beer and mix until well combined, then chill in the fridge for 24 hours.
Preheat the oven to 140C/275F/Gas 1.
Strain the beer from the beef mixture and set aside.
Season the beef cheeks with salt and freshly ground black pepper.
Heat a flameproof casserole dish, add the vegetable oil and brown the beef cheeks all over, then remove from the dish and set aside.
Reduce the heat, add the onions, carrots and garlic and cook for 4-6 minutes, or until pale golden-brown.
Add the herbs and peppercorns, then add the reserved beer and continue to cook until the volume has reduced by half.
Return the beef to the dish, add the chicken stock and bring up to the boil, then cook in the oven for three hours or until the beef is very tender.
For the parsley salad, place the shallot in a bowl, season with salt and freshly ground black pepper, add the lemon juice, olive oil and parsley.
To serve, spoon the cheeks onto serving plates, pile the salad alongside with a dollop of mash.