To bowl of blender, add tofu, plant milk, arrowroot starch, maple syrup, 1 Tbsp vanilla extract, salt, and cinnamon. Blend until completely smooth, stopping to scrape down sides of blender with rubber spatula, as needed. Pour mixture over bread. Using clean hands, flip and press bread down into liquid so all bread is evenly coated in tofu mixture. Sprinkle frozen berries overtop of bread. Cover baking dish with lid or piece of parchment paper, crimping it around edges of baking dish to secure. Place casserole in refrigerator for at least 1 hour and up to 12 hours.