Heat Oil: In a large pot, heat the olive oil or butter over medium heat. Add the onion and garlic, sautéing until soft and fragrant (about 5 minutes).
Add Potatoes: Stir in the diced potatoes and cook for 2–3 minutes.
Pour in Broth: Add the vegetable broth and bring to a boil. Reduce the heat and simmer for 10–12 minutes, or until the potatoes are tender.
Add Spinach: Add the fresh spinach leaves and cook for another 2 minutes, just until wilted.
Blend the Soup: Use an immersion blender or transfer the soup to a countertop blender (in batches if needed) to blend until smooth.
Add Cream: Stir in the heavy cream or coconut milk, then season with nutmeg, salt, and pepper to taste.
Serve: Pour into bowls, garnish with fresh parsley if desired, and serve warm with crusty bread or crackers.