Preheat oven to 425°F. Line a rimmed baking sheet with parchment paper or foil.

Arrange the leek, onion, parsnips, and garlic on the baking sheet, leaving room for the two halves of the romaine. Brush all with olive oil and season with a pinch of salt. Roast for 20 minutes.

When there's 8 minutes left, brush the romaine halves with olive oil and add them to the baking sheet.

The vegetables and romaine are ready when their edges are a golden brown. Remove from oven.

Meanwhile, bring the broth in a medium soup pot to a gentle boil, then reduce to medium-low and let settle for a few minutes.

Spoon the miso into a small prep bowl, and add a few tablespoons of the hot broth, stirring until the miso has dissolved. Add the miso and rice vinegar to the pot.

Add the kale and spinach leaves and cook until the leaves have wilted, but are still bright green.

Scrape the roasted vegetables into the broth. Stir and taste for saltiness. Add in small amounts until the soup has a gentle pop of bright flavor.

Puree the soup in a blender (you might need to do this in batches; I have a standard blender and didn't have to). Don't hesitate to let the blender run for several minutes. (Be careful of the top, which will want to fly off because of the hot pressure inside.) You'll see the bits of kale get smaller and smaller, until they look like flecks of pepper in the liquid.

Return the soup to the pot and heat through again. Taste, and add a sprinkle of lemon juice, and more salt, as needed.

Serve immediately, with a drizzle of fruity olive oil, and top garnishes such as fresh, chopped parsley, radish sprouts, or pomegranate seeds.