Preheat oven to 350°F. Place ½ cup each cashews and water in a microwave-safe bowl; cover and microwave on high for 3 minutes; let cool. Transfer to a blender, add cup broth, and blend until very smooth.
Heat oil in a large pot over medium-high. Add onion and garlic and cook, stirring, until softened, 2 to 3 minutes. Add cauliflower and cook, stirring, until golden, about 5 minutes.
Add beans, thyme, oregano, salt, pepper, and remaining 2 ½ cups broth. Bring to a simmer and cook, covered, for 10 minutes.
Toast remaining ¼ cup cashews on a baking sheet until golden, about 6 minutes; chop and set aside.
Add cauliflower mixture to blender and puree until smooth. Serve soup topped with toasted cashews, a drizzle of oil, and several grinds of pepper.
