Preparation

• In a large baking dish, liberally salt the pork shoulder. Refrigerate uncovered 1 hour.
• Preheat the oven to 425 degrees.
• Coat the pork with 2 tablespoons canola oil. Roast 2½ hours, until the skin is crisp and a meat thermometer inserted into the thickest part reaches 187 degrees. Let rest until cool enough to handle, then roughly chop into 2-inch pieces. Set aside.
• Meanwhile, in a cast-iron skillet over medium heat, saute the chorizo until the fat renders, about 4 minutes. Add the roast pork pieces and simmer 5 minutes. Remove from heat and set aside.
• In the bowl of a food processor, purée the loaded nachos into a thick paste. Scoop 1 cup nacho purée into a large mixing bowl and whisk in the milk. Add the flour to the mixture and fold with a rubber spatula until a pliable dough forms. Use your hands to roll the dough into golf ball-sized balls, then flatten into discs.
• Heat the remaining ½ cup canola oil in a cast-iron skillet over medium heat. (The oil is hot enough when a bit of dough sizzles in the pan.) Working in batches, fry the arepas until crisp and golden on 1 side, about 2 minutes. Flip and fry another 2 minutes. Remove and drain on a paper towel-lined plate.
• To serve, top each arepa with the pork mixture. Squeeze lime juice over each serving.