Asparagus Tip: When buying asparagus, look for firm, bright green spears with tightly closed tips.

In a large saucepan or Dutch oven, melt butter and saute shallots over medium-high heat until tender, about 4-5 minutes. Add flour and cook, stirring constantly for about 3-5 minutes. Stir in 1/3 cup of reserved asparagus cooking liquid until mixture is smooth. Add asparagus, milk, salt and pepper and bring to a boil. Quickly whisk a cup or so of the hot liquid into the sour cream to temper the cream before mixing back into the soup. Cool slightly before processing soup until smooth, in batches, in a food processor or blender. Reheat but do not boil, before serving.