01 - Preheat the oven to 425°F. Toss broccolini with 1 tablespoon olive oil, salt, and pepper. Arrange on a baking sheet and roast for 15–18 minutes, until lightly charred and tender. Set aside a few florets for garnish.
02 - Heat the remaining 1 tablespoon olive oil in a large pot over medium heat. Add the onion, celery, and potato. Sauté for 5 minutes until softened.
03 - Add garlic, thyme, oregano, and chili flakes (if using) and cook for 1 minute until fragrant.
04 - Stir in the roasted broccolini, beans, and vegetable broth. Bring to a boil, then reduce heat and simmer for 15 minutes until vegetables are very tender.
05 - Remove from heat. Using an immersion blender (or in batches in a countertop blender), blend the soup until completely smooth.
06 - Stir in the plant-based milk and lemon zest. Reheat gently if needed. Adjust seasoning with salt, pepper, and lemon juice to taste.
07 - Ladle soup into bowls. Garnish with reserved broccolini, a drizzle of olive oil, and extra chili flakes if desired.