Preheat oven to 375°F (190°C).
Prepare sauce: Blend cashews, milk, nutritional yeast, lemon juice, mustard, garlic, onion powder, paprika, salt, and pepper until silky.
Combine cooked rice and broccoli in a large bowl; pour in creamy sauce and fold gently to coat.
Assemble mixture in casserole dish; sprinkle shredded vegan cheddar evenly on top.
Bake uncovered for 25–30 minutes until edges bubble and cheese turns golden.
Optional finish: Sprinkle vegan Parmesan and return to oven 3 more minutes for extra crust.
Rest 5 minutes before serving so the gooeyness sets.