Chop asparagus: While the broth cooks, chop the spears into small pieces. Keep the heads separated in a small container.
Pot: After straining the broth, wipe the pot clean with a kitchen towel.
Roux: Melt the butter, add the chopped leeks (or shallots/onions) and a pinch of salt, and cook them gently until softer, but don’t let them take any color, about 2-3 minutes. Sprinkle the flour on top and stir everything for about 2 minutes.
Add broth: Slowly add the broth while whisking continuously to avoid any clumps forming. Once you’ve added all the broth, add the asparagus pieces (not the heads).
Cook soup: Cover, bring to a simmer, lower the heat and cook on medium-low heat for about 20 minutes or until the pieces are soft.
Blend: Add the heavy cream and blend the soup.
Asparagus tips: Return the soup to the stovetop, add the asparagus tips and reheat gently for 4-5 minutes; the heads of the plant should remain crunchy and not get very soft.
Adjust the taste with salt, pepper, nutmeg, and a little lemon juice (or white balsamic vinegar) to balance the flavors.