In a saucepan, melt the butter over medium heat. Add the chopped onion and garlic, saut? until translucent.

Add the asparagus pieces and diced potatoes, stirring for a few minutes.

Pour in the vegetable broth, bring to a boil, then reduce heat and simmer for about 20 minutes until the vegetables are tender.

Using a blender, puree the soup until smooth. Return to the pot.

Stir in the heavy cream, salt, pepper, and lemon juice. Heat through and serve warm.