Step 1Heat the oven to 375 degrees.
Step 2Combine the cornmeal, flour, sugar, baking powder, baking soda and salt in a mixing bowl and toss with a fork to blend. Combine the buttermilk, oil and 2 of the eggs. Pour the wet ingredients into the dry ingredients and stir until thoroughly mixed but still lumpy. Oil a 9-inch-square baking dish and heat it in the oven for 2 to 3 minutes. Pour the batter into the pan and bake 20 to 25 minutes, until browned and firm. Cool completely before proceeding.
Step 3Cut the cornbread into 1-inch cubes and place in a large mixing bowl. Add the onion, celery, red pepper, sage and parsley.
Step 4Melt 6 tablespoons butter in a large saute pan over medium heat. Add the garlic and saute until softened, about 2 to 3 minutes, then add the shiitakes. Cook until soft but not browned, about 10 minutes. Transfer the garlic-mushroom mixture to the bowl with the cornbread.
Step 5Melt the remaining butter in the saute pan and brown the sausage. Add it to the cornbread mixture. Toss until the ingredients are well blended, then season lavishly with salt and pepper to taste. Cool completely.
Step 6Fill the neck and body cavities of the turkey with the stuffing.
Step 7Beat the remaining eggs with the milk and mix with the remaining stuffing. Transfer the pudding mixture to a shallow nonstick baking dish and bake at 350 degrees until set, about 30 minutes.