Sweat the aromatics. Warm the olive oil in a medium pot over medium heat. Add the onion and a pinch of salt. Cook 5–7 minutes, stirring, until soft and translucent, not browned. Add the garlic and cook 30 seconds until fragrant.

Build body. Stir in the diced potato (or white beans) and pour in the broth. Bring to a simmer, then cook 8–10 minutes, until the potato is tender when pierced.

Add the greens. Turn the heat to low. Add the spinach in batches, stirring so it wilts quickly. Add the basil. Cook just until the leaves are bright and softened, about 1–2 minutes. Do not overcook or the color will dull.

Blend smooth. Take the pot off the heat. Blend with an immersion blender until silky. Or carefully blend in a countertop blender in batches, venting the lid and covering with a towel to release steam. Return soup to the pot if needed.

Season and brighten. Stir in lemon juice. Taste and add salt and pepper. For a richer bowl, swirl in Greek yogurt or coconut milk. Adjust acidity with more lemon if desired.

Serve. Ladle into bowls. Finish with a drizzle of olive oil, a crack of pepper, and a few torn basil leaves. Add Parmesan or red pepper flakes if you like a kick.