Combine beef, vegetables, herbs, and peppercorns in a bowl with beer and chill for 24 hours.
Preheat the oven to 140°C.
Strain the beer from the beef mixture and set aside.
Season the beef cheeks with salt and pepper.
Brown the beef cheeks in vegetable oil in a flameproof casserole dish and set aside.
Sauté the onions, carrots, and garlic in the same dish for 4-6 minutes.
Add herbs, peppercorns, and reserved beer, then reduce the liquid by half.
Return beef to the dish, add 1L chicken stock, and braise in the oven for three hours.
Mix shallot, lemon juice, olive oil, and parsley in a bowl to make the salad.
Serve beef cheeks topped with salad and a side of mash.