In a large pot, melt 2 tablespoons of butter over medium heat. Add 1 finely chopped onion and 2 minced garlic cloves, cooking for about 5 minutes until they are fragrant and translucent.

Incorporate 4 diced Russet potatoes into the pot, stir with onions and garlic, then pour in 4 cups of vegetable broth. Bring to a gentle boil, cover, and simmer for 15-20 minutes.

Gently fold in 4 cups of fresh spinach and allow to wilt, stirring for about 2-3 minutes.

Remove the pot from heat and puree the soup until smooth using an immersion blender.

Return the blended soup to the pot over low heat. Gradually whisk in 1 cup of heavy cream and another tablespoon of butter.

Taste and season with salt, pepper, and a pinch of nutmeg. Stir well.

Ladle the soup into bowls and garnish with freshly grated Parmesan cheese and chopped fresh herbs like thyme or chives.