After our dinner of grilled asparagus and sage polenta, we still had about a pound of asparagus left, but we had a plan. As we’ve remarked many times, we make stock at least once a week for homemade soup, and, this time, we figured a batch of cream of asparagus soup would be perfect.
We didn’t have a recipe specifically for cream of asparagus soup, but we do have a great recipe for cream of mushroom soup, and it’s a simple enough change (nearly all cream soups are the same, so once you have a recipe you like, just swap out an ingredient or two to make a new flavor).
Try to get the freshest, most local asparagus as you can. Once picked, the flavors in asparagus start to deteriorate, so that stuff that comes from South America generally only looks like asparagus. For the cream, we try to buy heavy cream that doesn’t have diglycerides or carrageenan. We don’t think cows are starting to add either of those to their cream; it must be someone else. For us, that means organic heavy cream, and in our case that means the cream hasn’t been ultra-pasteurized, which destroys some of the proteins and changes the taste. If you don’t have (or want to get) leeks for this soup, you can use some mild onion as a substitute. We just like the taste of leeks in cream soup, so we went with that.
Procedure in detail:
Prepare asparagus. We want the tips of asparagus for accent, so trim those off and set aside for later. Then, if you haven’t already done so, snap off the stems to remove the woody part. We kept the woody part to make stock sometime that week. Cut the remaining stalks into pieces between 1/2 inch and an inch long. Basically, small enough that they can be blended easily, yet large enough that it’s not a lot of trouble to transfer them to the soup pot later.
Cook leeks. Melt butter in a large saucepan over medium heat. Add leeks and cook, stirring often, until tender, about 10 minutes. If you wish, sprinkle just a touch of kosher salt while they’re cooking to draw out the liquid.
Add garlic and thyme. Stir the garlic and thyme into the leeks and cook until the garlic becomes somewhat tender, about a minute or two. Don’t cook anything so long that it starts to caramelize; for the color of this cream soup, we want to have mainly the green from the asparagus, not the leeks and garlic.
Add flour. Sprinkle the flour over the leeks while you stir it in. The flour will form a paste — technically a roux — in the bottom of the pan. Once incorporated, cook the flour for about a minute, but don’t let it brown.
Add broth and asparagus. While stirring the leek mixture, slowly add the broth. We like to add the broth in three additions, which seems to help prevent lumps. Once the broth is added, add the stems of asparagus (not the tips, those we’ll deal with in a moment) and bring to a low boil, stirring often. Reduce heat and simmer, stirring often, for 10 to 15 minutes.
Blanch and shock tips. While the soup is simmering, bring a pot of salted water to a rolling boil. Add the asparagus tips and boil for 3 to 5 minutes, or until tender. The amount of time will depend on the thickness of the tips. Once cooked, drain and immediately rinse with cold water to stop the cooking and lock in the bright green color.
Blend. Working in batches if necessary, blend the soup until very smooth. This may take several minutes depending on your blender, and remember: hot liquids can make the top of the blender pop off, so it’s best to vent the lid a little and hold it in place with a clean towel. Once blended return to the saucepan over medium-low heat.
Add cream and tips. Stir in the cream and the asparagus tips and slowly heat through. You don’t want to simmer the soup, just heat it, so stir and check often.
Season. Taste, and add salt and pepper as needed. Since we used scratched stock (no salt), we had to add one to two teaspoons of kosher salt to get the desired flavor. Pepper was probably about 1/4 of a teaspoon. Oh, and this would be a place to use white pepper if you have it.
Serve. Serve immediately, sprinkling a bit of black sesame seeds on top for garnish.
We loved this soup. Creamy and amazingly smooth, with a good asparagus flavor. We liked using the leeks; they were mild enough to add to the flavor, without overwhelming the delicate asparagus flavor. If there was anything we would do differently in the future, we would use more asparagus, probably about 1.5 pounds for four servings instead of just a pound. A five-star soup.