Butter a 13x9 baking dish and arrange sliced bread in rows. Whisk all ingredients, not including topping, in a medium bowl. Pour over bread. Cover and chill at least 2 hours (can be soaked one day ahead - keep chilled). Preheat oven to 375 degrees. Pulse all topping ingredients except syrup until nuts are coarsely chopped. Sprinkle over soaked bread. Place dish on a rimmed baking sheet and cover tightly with foil. Bake until warmed through, 25-30 minutes. Remove foil and bake 35-40 minutes longer or until browned. Serve with Blackberry Patch Blackberry Syrup.