In a small bowl, whisk together the miso, honey, soy sauce, rice vinegar, ginger, garlic, chile-garlic sauce, 1 tablespoon oil and 1 tablespoon water; refrigerate half of the marinade for serving.
Place the chicken in a shallow dish or zip-lock bag; pour the remaining marinade over the top; toss the chicken until coated and let marinate in the refrigerator for up to 30 minutes; a longer marinade time may dry out the chicken.
When you are ready to cook, heat the broiler with a rack set 6-inches below the heating element and line a large baking sheet with aluminum foil.
Remove the chicken from the marinade, scraping off and discarding any excess.
Place the chicken in a single layer on one side of the baking sheet, with the flatter side up.
Place the asparagus on the other side; drizzle the asparagus with remaining oil; season the asparagus; toss to coat.
Broil until the chicken is cooked through with some charred spots and the asparagus is browned; about 10 minutes.
To serve, top the chicken with a drizzle of the reserved marinade and a sprinkle of scallions; serve with rice, if desired.
