Heat the olive oil in a large saucepan over medium heat until shimmering and fragrant. Add the chopped onion and cook for about 5-7 minutes, stirring occasionally, until translucent and soft.
Add the minced garlic to the onions and cook for another 1-2 minutes until fragrant, being careful not to let it burn.
Toss in the chopped spinach and cook for 2-3 minutes until wilted and vibrant green, stirring occasionally to help it break down.
Pour in the vegetable broth, bring the mixture to a gentle simmer, then cover and cook for about 10 minutes to let the flavors meld.
Remove the pan from heat. Using an immersion blender or carefully transferring to a blender, purée the soup until smooth and velvety, about 1-2 minutes.
Return the puréed soup to low heat and stir in the heavy cream. Warm gently for about 3 minutes, tasting and adding salt and pepper as needed.
Finish by stirring in the freshly grated nutmeg, which will add a warm, spicy aroma to the silky soup.
Let the soup rest for a minute off the heat, then ladle into bowls and serve hot, garnished with a drizzle of cream or a sprinkle of black pepper if desired.
