Asparagus Soup

2 pounds fresh asparagus, rinsed and bottoms cut off
1 onion, peeled and halved
2-3 cups chicken or vegetable broth
2 Tbsp. butter
1/4 cup flour
2 tsp. salt
1 tsp. pepper
1 cup milk
1 cup sour cream
2 tsp. lemon juice

shredded cheese, for topping

Bring 2 cups of broth to a boil in a large pot; add asparagus and onion, cover, and simmer until asparagus is tender, 10 to 15 minutes.
Transfer mixture to blender and blend until smooth, adding more broth as necessary.
Meanwhile, in pot used to cook the asparagus, melt butter over medium heat. Whisk in flour, salt, and pepper. Whisk in milk and cook for a few minutes, whisking constantly until smooth.
Add pureed asparagus mixture to the saucepan and whisk to combine.
Bring to a simmer and cook for a few minutes, or until desired consistency is reached. If it's too thick, stir in some extra broth.
Whisk in sour cream and lemon juice.
Serve hot with shredded cheese of choice on top (we prefer sharp cheddar).