Brush the baguette cubes with garlic butter and toast under oven broiler, turning once, so they are golden brown on all sides. Steam all vegetables except cauliflower in water until softened but still crunchy ("Take one out and try it after a minute or two," says Oswald). Steam the cauliflower in a mixture of water and milk ("Cauliflower can have a strong smell, and the milk takes it away"). When all vegetables have been steamed, sauté in garlic butter for one minute. Sprinkle with chopped herbs. Set aside. To make slurry, dissolve cornstarch in water until the mixture resembles milk.