Cut the top 1 +1/2 inches off your spears . Cut the bottom inch off of the remaining portion of spears and discard. Peel the next inch up from bottom, (that part is usually a little tough) then cut into 1/2 inch pieces.
In a pot of salted boiling water cook asparagus tops for about 3 minutes or until tender. Remove to ice water to stop cooking process, drain and cut into 1/4 inch pieces.
In a medium soup pot, cook onions in butter over medium heat, covered , stirring often, Until translucent, about 7 minutes. Add potatoes and broth, bring to a boil and cook 1 minute. Add the center pieces of asparagus and cook 8 minutes or until potatoes and asparagus are tender. Cool .
In a blender puree soup, until smooth. There should be no need to strain unless desired.
Season with salt and pepper. Return asparagus tops, and serve. Hot or cold.