In a blender, combine shallots, lemongrass, fish sauce, oyster sauce, lime juice, maple syrup, brown sugar, ginger, garlic, sesame oil, chili paste, ground coriander, and Chinese 5 spice. Blend until smooth and well mixed.

Place the sliced pork tenderloin in a bowl and pour the marinade over the top, ensuring each piece is coated. Cover and refrigerate for at least 4 hours, ideally overnight.

In a small saucepan over medium heat, combine rice vinegar, sugar, and water. Stir until boiling and the sugar dissolves. Remove from heat and pour the hot brine over shredded carrots and daikon in a glass jar. Let cool at room temperature for about 30 minutes.

Refrigerate for at least an hour to develop a tangy pickled taste.

Partially freeze the marinated pork for about 30 minutes until firm. Lay it flat between plastic wrap or parchment paper and pound to about 1/8 inch thick.

Preheat your grill or skillet over medium-high heat. Cook the marinated pork slices for about 2-3 minutes on each side until golden brown and slightly charred.

Transfer the pork to a plate and let it rest for a few minutes before slicing into strips.

Split your Vietnamese baguette in half lengthwise. Heat a grill pan or skillet and place the cut sides down to toast until crispy and golden, about 2-3 minutes.

Spread a generous layer of mayonnaise (and pâté, if using) on both sides of the toasted baguette. Layer with cooked pork, pickled vegetables, cucumber slices, jalapeños, and cilantro.

Slice the assembled sandwich in half and serve immediately.