Position 2 racks in the upper and lower thirds of the oven and preheat to 400 degrees F. Cut four 16-inch long sheets of parchment paper. Fold each sheet in half and open like a book. Divide the pieces of parchment between 2 baking sheets (2 pieces per sheet).
Trim away the tendon attached to the thicker part of the tenderloin with kitchen shears and discard. Sprinkle the chicken all over with 3/4 teaspoon salt.
Combine the soy sauce, sesame oil, rice vinegar, sambal, scallion whites, ginger, and 1 tablespoon water in a small bowl. Place snow peas and shiitakes in a medium bowl and toss with 2 tablespoons of the soy sauce mixture.
Mound 3/4 cup brown rice on each parchment sheet, placing it on one side of the fold, and drizzle with 1 tablespoon water. Top with the vegetables, and two chicken tenders per serving, tucking as many of the vegetables as possible under the chicken. Spoon about 2 teaspoons of the soy sauce mixture evenly over each serving of chicken. (You should have some left over for drizzling later.)
Fold over the top half of the parchment, crimping and overlapping small folds along the open edge to seal tightly. Bake until the parchment puffs, 18 minutes; chicken will be cooked through. Transfer the packets to plates and let stand 2 minutes. Avoiding the hot steam, carefully cut open the packets. Drizzle remaining soy sauce mixture over the chicken and rice. Top with scallion greens, cilantro, and sesame seeds.