Pre-heat oven to 350°F (180°C).
In a large skillet, heat ¼ cup (60 mL) of the butter and oil over medium-high heat. Sauté celery and onion for 5 minutes or until softened. Add sage and garlic and sauté for 2 minutes more. Remove from heat.
In a large bowl, combine onion mixture with bread and mix well. Toss bread mixture with stock to combine. Add feta, chestnuts and parsley and toss to combine. Season with salt and pepper to taste.
Grease a 13- x 9-inch (3 L) baking dish with remaining tablespoon (15 mL) of butter. Place stuffing mixture into baking dish. Bake uncovered for 45 minutes or until stuffing is hot and top is lightly golden brown.