Lomito

To make brining solution, place salt in a 5 litre non-reactive bowl, add 1litre boiling water and stir until salt dissolves. Add 3 litres cold water and the remaining ingredients. Refrigerate until completely cold. Add pork, ensuring it is fully immersed, then refrigerate for 12 hours. (Do not brine pork for more than 12 hours or it will absorb too much salt.) Drain and pat pork dry with paper towel.
Preheat oven to 150°C. Heat oil in a large, heavy-based, ovenproof saucepan over medium–high heat. Add pork and cook, turning, for 5 minutes or until browned all over. Add carrot, celery, bay leaves, beer, dill seeds, cloves, peppercorns and enough water to completely cover. Cover surface with a sheet of baking paper, then cover with a lid. Transfer pan to oven and cook for 2 hours or until pork is tender and cooked through. Transfer pork to a bowl, pour over half the liquid and cool to room temperature.
Increase oven to 180°C. Warm bread rolls in the oven for 5 minutes, then cut in half horizontally. Layer cheese on top half, then heat in oven for 5 minutes or until it melts.
Meanwhile, spread avocado over the base of each roll and top with jalapeños. Remove pork from the cooking liquid and, using a sharp carving knife, slice as thinly as possible. Divide among rolls. Top with tomatoes, if using, sauerkraut and chilli sauce, if using. Spread mustard and mayonnaise over melted cheese, then sandwich lomito and serve immediately.