1. Heat oven to 400 degrees . Distribute challah cubes in one layer over 2 sided baking sheets. Bake for 8 minutes, until lightly browned. Transfer to a large bowl.
2. Meanwhile, heat a skillet over medium-high heat. Add sausage, breaking apart with a spoon. Cook for 5 to 7 minutes, until browned. Reduce heat to medium. Stir in pears, onion and garlic; cook for 5 minutes. Stir in stock, scraping bottom of pan to release brown bits. Mix in pecans, thyme, sage, salt and pepper. Pour mixture into bowl with challah; stir until well combined. Transfer to a 13 x 9 x 2-inch casserole dish, pressing down a bit with a spatula. Cover dish with aluminum foil and bake at 400 degrees for 20 minutes. Uncover and bake another 5 minutes.