Melt butter in a large saucepan over medium heat. Add onions and garlic and cook for 1-2 minutes until tender. Add asparagus and cook an additional 5 minutes.
Stir in broth. Cover and let simmer 10-15 minutes or until the asparagus has softened.
Using a hand blender, puree soup until smooth. Remove from heat and stir in sour cream, lemon juice, and pepper to taste.
Notes
If using a regular blender to puree soup or hot liquids, do not seal the lid. The steam can build up creating a mess and burn hazard.
Fresh asparagus is key to making delicious asparagus soup. Look for firm, bright green stalks with tightly closed tips.
Trim off the tough woody ends of asparagus, which are not pleasant to eat.
To enhance the flavor of the soup, sauté onions and garlic in butter or oil before adding the asparagus.
Achieve a luxurious, creamy texture with heavy cream or half-and-half.
Consider adding other herbs and spices, such as thyme, rosemary, or nutmeg, to enhance the flavor.
A sprinkle of chopped fresh herbs, such as chives or parsley, or a swirl of crème fraîche or sour cream can add a beautiful touch to creamy asparagus soup.