- 2 tablespoons extra-virgin olive oil
- 1 medium onion, chopped
- 1 large bunch thin asparagus (about 20 stalks), thinly sliced
- 1/4 cup spinach leaves
Bring a small saucepan filled with water to a boil over high heat. Prepare an ice-water bath; set a medium bowl in ice-water bath and set aside.
Heat olive oil in a large shallow saucepan over medium-low heat. Add onion and reduce heat to low; cook, until onion is soft and translucent, about 10 minutes. Increase heat to medium-high and add asparagus; stir to coat.
Add enough boiling water just to cover asparagus; let cook for 2 minutes. Drain asparagus mixture in a fine mesh strainer and transfer to bowl set in ice-water bath; let cool slightly.
Transfer asparagus mixture to the jar of a blender along with spinach leaves. Add enough water just to blend; blend until smooth.