Make the stuffing:
(This dish can be prepared up to two days ahead or made while the turkey is baking.)
1. In a large skillet, melt 1 Tbsp butter over medium heat. Add the sausage, and cook for about 5 minutes. Remove with a slotted spoon, and set aside.
2. In the same skillet, add the onions and celery. Season with salt and pepper. Cook the vegetables over medium heat, stirring occasionally, until translucent, 8 to 10 minutes. Set aside with the sausage and reserve the skillet.
3. Toast the bread. Cut into 1-inch squares, and transfer to a large bowl. Melt the remaining butter. Toss the bread with the butter, thyme, sage, and rosemary.
4. In the skillet, sauté the pepperoni over medium-high heat until oils are released, 2 to 3 minutes. Remove and drain.
5. Toss the sausage, celery-and-onion mixture, pepperoni, and mozzarella with the bread. Then add the chicken stock to moisten the ingredients. Place the stuffing in a casserole dish, cover with foil and refrigerate until ready to bake.
6. Bake with the turkey. Remove the cover for the last 15 minutes, or until the top is golden brown. Drizzle with turkey drippings to keep moist, if you like.
Ideas for picky eaters: If your child won't go for the unfamiliar stuffing, try reserving and baking a little of the toasted-bread-and-vegetable mixture without meat and cheese for her own special batch.