Prepare the pickle: Peel both the carrot and the daikon. Cut into matchsticks about 3 inches long and about as wide as the fattest part of a chopstick; place in a bowl. Add the salt and 1 tsp of the sugar. Using your hands, massage the carrot and daikon for about 3 minutes. This expels the water and softens the veg. They’re perfectly softened when you can bend a daikon matchstick in half and make the ends touch without snapping the stick. Drain the mixture and rinse; press to remove excess water. Return mixture to bowl or a jar.
In a large measuring cup or bowl, whisk the remaining sugar with the vinegar and until dissolved. Pour the mixture over the vegetables (it should cover the vegetables). Allow the mixture to marinate for at least 1 hour before serving. It will keep in the fridge for up to 4 weeks.
Prepare the chicken: Trim and flatten the thighs. Place the chicken in a glass baking dish or a large zip-top bag. In a bowl, whisk together all the remaining ingredients then pour over chicken. Allow to marinate in the fridge at least 3 hours, or up to 1 day, before grilling.
Allow chicken to return to room temperature before grilling. Preheat an outdoor grill or indoor grill pan over medium-high heat. Grill the chicken about 3 to 4 minutes a side or until cooked through (165°F)
Allow to rest about 5 minutes then slice against the grain. Keep warm until ready to use.
Prepare the rolls: Preheat an oven to 325°F. Bake the sandwich rolls for about 8 minutes until the outside is crisp and they sound hollow when tapped. Allow to cool before serving.
Meanwhile, prepare the aioli: In a blender or a mixing cup for an immersion blender, add the egg, sriracha, and salt. While the blade is running, slowly drizzle in the oil; continue blending until the mixture is emulsified. Set aside.
To Build the Bánh Mì: Drain servings of the pickle and pat dry. Without slicing all the way through, slice the rolls lengthwise (leave a hinge). Scoop out a little of the bread (to better fit ingredients inside, my dear!), then spread some of the aioli all over the inside of the roll then lightly dash a bit of soy sauce or liquid aminos on top. Layer on the chicken, the pickle, the cucumber, jalapeño and the herbs. Close up that Bánh Mì, serve remaining aioli on the side and dig in!