To prepare polenta, place broth and milk in a saucepan and bring to a boil over medium-high heat. Add polenta, whisking to prevent clumping. Reduce heat to low and cook, stirring constantly, until liquid is absorbed and polenta is creamy and thoroughly cooked, 5 to 10 minutes.
Add cheese, butter and salt, stirring gently until incorporated.
To prepare the greens, using a slotted spoon, scoop one cup of Roasted Garlic into a very large skillet over medium-high heat. Add bok choy and sauté 3 minutes. Add spinach and sauté 2 minutes. Add salt and pepper. Serve over polenta.