Roll cut the asparagus ends to expose the center, and chop the onion.

Place the vegetables in a saucepan with the milk, and bring to a simmer. Continue to simmer for 20-30 minutes, until asparagus stems are completely tender. Let cool in the milk.

Pour mixture into blender jar, and blend on High for several minutes, until completely liquefied.

Pour through a fine strainer into a bowl, using a silicone spatula to press liquid and puree through. Discard the fibrous mass left in the strainer.

Return to a pot, and bring to a low boil, stirring frequently. Add Roux Cubes, and stir until they dissolve, and then until the soup is lightly thickened.

Serve at once.