Chicken Hot Pot with Mushrooms and Tofu

Name: Chicken Hot Pot with Mushrooms and Tofu
Ingredients: 12 cups chicken stock or low-sodium broth; 1 pound honshimeji or cremini mushrooms—stems removed and reserved, caps thinly sliced; One 2-inch piece of ginger, thinly sliced; 2 large garlic cloves, crushed; Kosher salt; 6 skinless, boneless chicken thighs (about 1 3/4 pounds), trimmed and sliced into 1/4-inch strips; One 14-ounce package firm tofu, drained and cut into 1/2-inch dice; 4 scallions, thinly sliced; Asian sesame oil, for drizzling