1 pound fresh asparagus, tough ends broken off
3/4 cup chopped onion
1 3/4 cup vegetable or chicken broth, divided
1 tablespoon butter
2 tablespoons all-purpose flour
1 teaspoon salt
1 pinch ground black pepper
1 cup milk
1/2 cup yogurt or sour cream
1 teaspoon lemon juice
1/4 cup grated Parmesan cheese

Place asparagus and onion in a saucepan with 1/2 cup broth. Bring the broth to a boil, reduce heat and let simmer until the vegetables are tender.

Reserve a few asparagus tips for garnish. Place remaining vegetable mixture in a blender or food processor and puree until smooth.

Melt butter in the pan that was used for simmering the asparagus and onions. Stir while sprinkling flour, salt, and pepper into the butter. Do not let the flour brown. Allow the mixture to cook exactly 2 minutes. Stir in remaining 1 1/4 cups broth and increase the heat. Continue stirring until the mixture comes to a boil.

Stir the vegetable puree and milk into the saucepan. Whisk yogurt into the mixture, followed by lemon juice. Stir until heated through, then ladle into bowls. Garnish with reserved asparagus tips. Sprinkle with Parmesan cheese if desired.