Arrange bread cubes on prepared baking sheet and spray with cooking spray. Sprinkle cubes with parmesan cheese. Bake for 10 to 15 minutes, or until golden brown.
While the croutons are baking, heat oil in a large saucepan over medium heat. Add leeks and garlic and cook for 2 minutes, or until soft. Add bay leaves and thyme and cook for 1 minute, or until fragrant. Add asparagus, potato and broth and bring to a simmer. Reduce heat to medium, partially cover and simmer for 10 minutes, or until potato is fork tender. Remove bay leaves, and using an immersion blender, or a regular *blender working in batches, puree soup until smooth. Ladle soup into bowls and top with sundried tomatoes and croutons.
When blending hot liquid, first let it cool for five minutes or so, then transfer it to a blender, filling only halfway. Put the lid on, leaving one corner open. Cover the lid with a kitchen towel to catch splatters, and pulse until smooth.