- Prepare the Asparagus: Wash the asparagus thoroughly and trim off the tough ends. Cut the asparagus into 2-inch pieces, discarding any woody parts. 
- Sauté the Onion and Garlic: Heat a large soup pot or pan over a medium heat and spray it with low-calorie cooking spray. Add the  onion and garlic and sauté for about 2-3 minutes until the onion becomes translucent and fragrant. 
- Add Potatoes and Asparagus: Add the diced potatoes and asparagus to the pot and stir well with the onions and garlic. 
- Pour in the Stock: Pour in the vegetable stock, ensuring that the potatoes and asparagus are submerged. Bring the mixture to a boil. 
- Simmer: Reduce the heat to low, cover the pot, and simmer for about 15-20 minutes or until the potatoes and asparagus are tender. 
- Blend: Using an immersion blender, carefully blend the soup until it's smooth and creamy. If you don't have an immersion blender, you can transfer the soup in batches to a blender, but be sure to let it cool slightly before blending to avoid splattering. 
- Add Milk: Return the blended soup to the pot, and stir in the skimmed milk. Cook for an additional 5 minutes over low heat, stirring frequently. 
- Season: Season the soup with salt and black pepper to taste. Adjust the seasoning as needed. 
- Serve: Ladle the hot soup into bowls. Garnish with chopped fresh chives if desired.