Heat a large pot over medium heat and add the olive oil. Once shimmering, add the diced onion and sauté until it becomes translucent and fragrant, about 5 minutes.
Add the minced garlic to the pot and cook for another minute, until the garlic releases its aroma and slightly softens. Be careful not to let it brown.
Pour in the vegetable broth, bringing the mixture to a gentle simmer. Add the chopped spinach, stirring until it wilts and reduces in volume, about 2-3 minutes.
Use an immersion blender or transfer the mixture carefully to a blender and blend until completely smooth and velvety. Return the soup to the pot if using a stand blender.
Stir in the heavy cream and chopped mint, then season with salt and pepper to taste. Warm the soup gently over low heat, about 5 minutes, allowing the flavors to meld.
Adjust the seasoning if needed, then serve hot. Garnish with a small sprig of mint or a drizzle of cream if desired for a beautiful presentation.
