In a large stock pot heat the olive oil and add the onion and salt. Cover, stirring occasionally until the onions are very soft. Add the white cooking wine and garlic. Increase heat and cook until the liquid is completely evaporated. Add the cauliflower and chicken broth. Return to a boil, then reduce heat to simmer. Cover and cook for 20-25 minutes or until the cauliflower is very very tender.
Meanwhile preheat oven to 415 degrees F. Place slices of crusty baguette onto a baking sheet and drizzle with olive oil. Sprinkle with asiago cheese and bake for 10 minutes or until the cheese has started to brown slightly around the edges, and the bread is crispy.
Once the cauliflower is tender use an immersion blender to blend the soup to a creamy consistency. Or alternatively, blend the soup in batches in a blender until smooth. Serve with a crouton on top, and you can sprinkle more asiago cheese on top if you prefer.