Sauté the aromatics: Warm 1–2 tablespoons of olive oil in a large pot over medium heat.
Add the onion and a pinch of salt. Cook 4–5 minutes until translucent. Stir in the garlic and cumin, and cook 30–60 seconds until fragrant.
Add the vegetables: Toss in the chopped broccoli and the potato (or white beans).
Stir to coat with the oil and aromatics for about a minute.
Pour in the broth: Add 4 cups of vegetable broth. Bring to a gentle boil, then reduce to a simmer. Cook 10–12 minutes, until the broccoli and potato are tender.
Wilt the spinach: Add the spinach in batches, stirring until it wilts.
This takes 1–2 minutes. Turn off the heat.
Blend until smooth: Use an immersion blender to blend the soup right in the pot until silky. Or carefully blend in batches in a countertop blender.
Return to the pot if needed.
Brighten and season: Stir in lemon zest and 1–2 tablespoons of lemon juice. Add chopped parsley if using. Taste and adjust with salt and pepper.
Serve: Ladle into bowls and finish with a drizzle of olive oil, a spoonful of yogurt, a pinch of chili flakes, or toasted pumpkin seeds for crunch.