Cut the pork into long strips about 1 ½ inches wide. In a medium bowl, combine the packet of seasoning mix with the water and stir to dissolve. Add the pork and toss to coat. Cover with plastic wrap and refrigerate overnight.

While the pork is marinating, make the paté. Heat the butter in a medium saucepan over medium high heat and sauté the livers together with the onion and green onions until onion is translucent. Add the chicken stock, fish sauce, and black pepper, bring to a simmer, and cook until the livers are cooked through, 8 to 10 minutes. Remove from the heat and strain the livers in a coarse sieve (reserve cooking liquid separately). Transfer the livers and vegetables to the bowl of a food processor and allow to cool briefly, then process until smooth, adding as much of the cooking liquid as necessary to form a smooth mixture.  Taste and adjust the seasoning if necessary. Set aside to cool, then refrigerate, covered, until ready to make the sandwiches, up to several days in advance.

To make the pickled carrots, combine the vinegar and sugar in a medium saucepan and bring to a boil. Stir until the sugar is dissolved, then remove from the heat and allow to cool. Once cooled, transfer the vinegar mixture to a nonreactive bowl and add the carrots and garlic. Refrigerate until ready to make the sandwiches, up to several days in advance.

When you are ready to make the sandwiches, preheat the oven to 400°F. Remove the pork from the marinade and pat dry. Discard marinade. Place the pork on a foil-lined baking sheet and bake (uncovered) for 20 minutes. Remove from the oven and allow to cool briefly, then slice the pork crosswise into thin slices. (Alternatively, the pork may also be grilled or broiled until well-done.)

Place the bread in the oven until warmed through and slightly crisp – 1 to 2 minutes.

Spread the bottom cut sides of the bread with mayonnaise and divide the pork slices evenly among the sandwich bottoms. Top with the cucumber slices, pickled carrots, julienned jalapenos and cilantro sprigs.  Sprinkle lightly with soy sauce if desired. Spread the top cut sides of the bread with the paté and place on top to close the sandwiches. Serve immediately.