Melt butter in a large pot over medium heat. Add onion and cook until softened, about 5 minutes.

Add garlic and cook for 1 minute more.

Add asparagus and vegetable stock to the pot. Bring to a boil, then reduce heat and simmer for 20-25 minutes, or until asparagus is tender.

Carefully blend the soup using an immersion blender or transfer to a regular blender. Blend until smooth and creamy.

Stir in heavy cream and season with salt and pepper to taste.

Serve hot.