Carefully remove the stem and core of the cauliflower with a knife. Slice the core and stem thinly. Break off about a cup of nice-looking small florets, each 1/2 inch across at the largest, and set them aside in a bowl. Slice the rest of the cauliflower into 1/2-inch slices. Separate the sliced cauliflower into two equal batches.

Heat 3 Tablespoons of plant-based butter in a large pot over medium-low heat. When the butter is melted, add the onion and leek. Saute until the onion is translucent and tender, 7-8 minutes, stirring often. If either ingredient starts to brown at any point, reduce the heat slightly.

Add 4.5 cups of the water, the sliced cauliflower stem and core, and half the sliced cauliflower. Increase to medium-high heat until the water begins to simmer, then bring it back down to medium-low. Simmer for 15 minutes, then add the rest of the sliced cauliflower. Simmer until the second batch of cauliflower is tender, 15 minutes or so, stirring occasionally.

Melt the remaining 5 tablespoons of plant-based butter in a large skillet over medium heat. Add the cauliflower florets and pine nuts. Saute until the florets are lightly browned and the pine nuts are toasted, 5-7 minutes, stirring often to prevent the nuts from scorching. Add the paprika. Stir for 1 more minute to mix well and lightly toast the paprika.

Transfer the contents of the skillet to a bowl and stir in the vinegar.

Transfer the soup into portion-sized bowls. Divide the drizzle among the bowls, making sure to include some paprika oil, some cauliflower florets, and some pine nuts. Garnish with chives and serve immediately.