In large pot, heat 1 Tbsp olive oil over medium heat. Sauté onion until soft, about 5 minutes, then add garlic and cook for another 1 minute. Add cauliflower, white beans, nutmeg, broth, almond milk, salt, and pepper. Bring to a boil, reduce heat, and simmer for 20 to 25 minutes, until cauliflower is tender.
Toss sourdough cubes with olive oil, rosemary, salt, and pepper. Spread on baking sheet and bake in preheated oven for 10 to 12 minutes, until golden and crispy. Remove from oven to cool.
Line baking sheet with parchment paper. Place small mounds of Parmesan cheese on sheet and spread into thin circles. Bake in preheated oven for 5 to 6 minutes, until golden. Let cool and set aside.
Using immersion blender (or high-speed blender), purée soup until smooth. Adjust seasoning, if necessary.
Ladle soup into bowls; top with rosemary croutons and a Parmesan tuile.