Roasted Vegan Cauliflower Soup with Parsley-Chive Swirl

Preheat oven to 400 degrees F. Coat 2 large rimmed baking sheets with cooking spray.

Toss cauliflower and leeks with 1/2 cup oil and 1 1/4 teaspoons each salt and pepper in a very large bowl (you may need to do this in 2 batches). Divide the vegetables evenly between the prepared baking sheets. Roast, switching the pans from top to bottom and back to front halfway, until soft and browned on the bottom, 25 to 30 minutes.

Meanwhile, place parsley, chives and the remaining 1/2 teaspoon each salt and pepper in a blender; pulse several times to chop, scraping down the sides once or twice. With the motor running, slowly add the remaining 1 cup oil and process until smooth. Transfer to a bowl and rinse out the blender.

Transfer the roasted vegetables to a large pot and add broth. Bring to a boil over high heat. Reduce heat, cover and simmer for 10 minutes. Puree the soup in batches in a blender. (Use caution when pureeing hot liquids.) Stir in vinegar. Serve with some of the herb sauce swirled on top.