Special equipment: a sandwich press
Preheat a sandwich press to medium heat.
Drizzle the onion and pepper with the olive oil and season with salt and pepper. Put the onion and pepper on the sandwich press, close and cook until tender and lightly browned, 8 to 10 minutes. Slice into strips.
Brush the outside of the bottom half of the bread with some of the melted butter. Brush the inside of both halves with a generous amount of the Mojo Mustard. On the bottom half of the bread, layer the sliced deli ham and top with the carnitas. Top with the gherkins, grilled onion and peppers and finally the cheese. Top with the top half of the bread and brush with more butter. Slice in half widthwise.
Place both halves in the sandwich press, close, press down and cook until the bread is crispy and the cheese is melted, 5 to 7 minutes. Cut in half to make 4 sandwiches.
Mix together the mustard, honey, chili paste, oregano, cumin, orange zest and juice, lime zest and juice, garlic and some salt and pepper in a bowl.
Set the slow cooker to high. Put the pork cubes in the slow cooker and season all over with the chipotle powder and some salt. Turn any pieces with the fat cap upright. Nestle in the garlic, cinnamon sticks and yellow onion. Pour the orange soda, vegetable oil and orange juice and zest over the pork. Cover and cook on high until super tender, about 4 hours.
Preheat the oven to broil.
Transfer the pork chunks to a baking sheet fat-side up. Let the liquid in the slow cooker settle so the fat is on the surface. Scoop off about 1/4 cup of the fat and drizzle over the pork chunks. Broil until the meat is crispy and the fat is bubbly, 1 to 2 minutes.
You can substitute braised pork from the hot bar at the grocery or shredded rotisserie chicken for the carnitas.