In a shallow dish or large bowl, combine the sliced chicken breast, minced lemongrass, minced garlic, grated ginger, fish sauce, soy sauce, brown sugar, lime juice, sesame oil, and black pepper. Toss to coat the chicken evenly. Let it marinate for at least 15-20 minutes at room temperature, or up to 30 minutes in the refrigerator.

While the chicken marinates, prepare the pickled vegetables. In a small bowl, combine the julienned carrots and daikon radish. In a small saucepan, whisk together the rice vinegar, water, granulated sugar, and salt. Heat over medium heat, stirring until the sugar and salt dissolve (do not boil). Pour the warm pickling liquid over the vegetables. Let them sit and quick-pickle for at least 15-20 minutes, stirring occasionally.

In a small bowl, whisk together the fish sauce, lime juice, water, granulated sugar, minced garlic, and minced red chili (if using) until the sugar dissolves. Taste and adjust sweetness, sourness, or saltiness to your preference.

Preheat your air fryer to 375°F (190°C). Arrange the marinated chicken in a single layer in the air fryer basket (you may need to do this in batches). Air fry for 10-12 minutes, flipping halfway through, until the chicken is cooked through and lightly caramelized. (Alternatively, you can pan-fry the chicken in a skillet over medium-high heat with a little oil for 3-4 minutes per side until cooked through).

To assemble each bowl, place a portion of warm cooked brown rice at the bottom. Top with the cooked lemongrass chicken, a generous spoonful of the quick-pickled carrots and daikon (drained), fresh cucumber slices, chopped cilantro, and fresh mint (if using). Add thinly sliced jalapeño if desired for extra heat.

Drizzle generously with the prepared Nuoc Cham dressing. Garnish with crushed peanuts (optional) and serve immediately with a fresh lime wedge on the side.