Roughly grind the peppercorns and juniper berries in a mortar and stir in the paprika, caraway and salt. Add the garlic.
Rub the marinade onto the meat, wrap in cling film and chill in the fridge overnight. Remove from the fridge an hour before cooking and unwrap.
Heat the oven to 130°C | (110° fan)| 250°F | gas 1/2. Place the meat on a deep baking tray and add the beer. Cook in the oven for around 6 hours until the meat has a core temperature of 90°C (180°F). Regularly baste the meat with its juices and, if necessary, add a little water.
Once cooked, turn off the oven, cover the meat with aluminium foil and return to the oven for another hour.
Mix together the carrots and courgette with the lemon juice and oil. Season with salt and ground black pepper and fold in the lettuce and herbs. Halve the rolls and divide half the salad between them.
Pull the meat apart with a fork, mix with the meat juices and place on top of the salad. Add the remaining salad and cover with the lids of the rolls. Serve immediately.