In a bowl, whisk together rice vinegar, warm water, sugar, and salt until dissolved. Add julienned daikon and carrots, toss to combine. Let sit for at least 30 minutes, or refrigerate up to 1 week.
Marinate and Cook the Pork
In a bowl, combine minced garlic, lemongrass, fish sauce, soy sauce, brown sugar, and vegetable oil. Add sliced pork and marinate for at least 30 minutes.
Heat a large skillet over medium-high heat. Add marinated pork and cook 4-5 minutes per side until caramelized and cooked through. Remove from heat and let rest.
Assemble the Sandwiches
Preheat oven to 350°F. Warm baguettes for 2-3 minutes until crispy outside. Split lengthwise and lightly hollow out some interior bread.
Spread pâté on one side of each baguette and mayonnaise on the other. Layer with cooked pork, drained pickled vegetables, cucumber slices, cilantro, and jalapeños.
Close sandwiches and serve immediately while bread is still warm and crispy.
Notes
Storage tip: Components can be made ahead and stored separately. Pickled vegetables improve in flavor over time and keep up to 2 weeks refrigerated. Never store assembled sandwiches as bread will become soggy.