Wash and quarter the bok choy. Spray a sheet pan with oil and place the bok choy on the tray evenly spaced. Spread the miso tahini mixture over the bok choy. Cook in a 350F oven for 20 minutes.
Meanwhile, in a sauce pan heat the chicken stock, miso, tahini and pepper. Heat until tahini paste and miso are dissolved into the stock. Remove from heat and set aside.
Remove bok choy and spread sauce over the top and garnish with chopped peanuts. Serve immediately.