Heat the broiler with the rack in the upper third of the oven.
Toast the walnuts in a small pan over medium heat until fragrant.
Heat the EVOO, a turn of the pan, in a large skillet or Dutch oven with lid over medium-high heat. Add 3 tablespoons butter to the pan and melt. Then add the celery, carrots, bay leaf and onions. Next, season with salt, pepper and thyme. Partially cover the pan and sweat the vegetables for 7 to 8 minutes. Remove the lid, sprinkle the vegetables with the flour and stir 1 minute. Then whisk in 2 1/2 cups chicken stock and cook to thicken. Add the turkey and heat through. Reduce the heat to a simmer and remove the bay leaf.
Meanwhile, heat the remaining 1 1/2 cups chicken stock and the milk to a low boil. Whisk in the polenta and thicken, 2 to 3 minutes. Sprinkle the polenta with a little salt and stir in half of the Cheddar, the cranberry sauce, honey, orange zest, walnuts and the remaining 2 tablespoons butter. Spoon and spread the polenta over the top of the turkey filling and scatter the remaining Cheddar over top. Broil to brown and set the top, 1 to 2 minutes.