Chicken, Mushroom, and Brown Rice Slow Cooker Casserole

spray(s) cooking spray

uncooked boneless skinless chicken thigh(s) use eight 2 1/2 oz thighs

cup(s) canned chicken broth reduced-sodium

pound(s) cremini mushroom(s) sliced

cup(s) uncooked leek(s) white and pale green parts only, thinly sliced, washed carefully for grit

cup(s) uncooked carrot(s) thinly sliced

cup(s) uncooked celery thinly sliced

cup(s) uncooked long grain brown rice medium-grain (such as brown Arborio)

Worcestershire sauce

Dijon Mustard

dried sage

table salt

black pepper freshly ground