In a medium bowl, combine the lemongrass, shallot, ginger, garlic, brown sugar, oil, soy sauce, fish sauce, and lime juice. Season with a hefty pinch of kosher salt and ground black pepper. Mix to combine well, then reserve ½ of the marinade for serving. Add chicken to the bowl, tossing to coat in the remaining marinade. Set aside or cover and refrigerate for up to 2 days.
At dinnertime, prepare the grill for medium-high direct heat grilling, about 450-500 degrees F. Once hot, clean the grates by brushing firmly with a grill brush. While the grill heats, prep the spring roll bowl ingredients: slice the veggies and prep the rice vermicelli according to package directions; once tender, chill by rinsing well with cold water. Set aside for assembly.
Place the chicken on the preheated grill, discarding any excess marinade. Grill 4-5 minutes per side, or until cooked through. Transfer to a plate or small baking sheet and rest.
Once the chicken is cool enough to handle, thinly slice into strips and build your spring roll bowls as desired—I like to create a bed of rice noodles and lettuce, pile the veggies and chicken over top, then finish it off with lots of herbs, peanuts, and peanut sauce and/or reserved lemongrass marinade.
