Step 1

Fill a large pot with 2 cups water and fit with a steamer basket. Bring to a boil. Add the asparagus and steam until tender, 3 to 4 minutes. Remove the asparagus to a cutting board and pour the water from the pot into a large measuring cup; add more water if needed to equal 2 cups. Set the pot aside.

Step 2

When the asparagus is cool enough to handle, trim off the tips and halve lengthwise; toss with a pinch of salt. Save these pieces for garnish. Add the remaining asparagus pieces to a blender with 1 cup of the reserved steaming water and blend until very smooth.

Step 3

Melt the butter in the pot over medium heat. Add the onion and cook until it begins to soften, 3 to 4 minutes. Add the garlic and cook until fragrant, 30 seconds more. Sprinkle in the flour and stir to combine.

Step 4

Slowly whisk in the half-and-half and remaining 1 cup reserved steaming water until smooth. Season with 1 teaspoon salt and the coriander. Bring to a simmer and cook, stirring occasionally, until the mixture starts to thicken, 10 to 15 minutes.

Step 5

Stir in the asparagus puree. Taste and adjust the seasonings (add more salt if it needs it!) and let the soup heat through. Ladle into bowls and garnish with the asparagus tips. Season with pepper.