Trim the asparagus ends, peel the lower half with a peeler, and cut into 2cm pieces. Slice the potato into thin 5mm slices and soak in water, then drain. Thinly slice the onion.

Heat butter in a pot over medium heat, add onion and sauté until translucent for about 3 minutes. Add potato and stir until coated with butter.

Add water, consomme, and salt. Bring to a boil, cover, and simmer on low heat for 8 minutes. Add asparagus and cook for another 3 minutes. Let cool slightly.

Blend the mixture in a blender until smooth. Return to the pot, add milk, and heat gently over low heat.