Why It Works
- Fennel reinforces the anise-like flavor of tarragon.
- A flour-thickened velouté delivers brighter vegetable flavor than a cream-based soup.
In classical French cuisine, velouté is technically a sauce made by thickening stock with a butter- and flour-based roux (think béchamel with stock instead of milk). These days, if you see the word on a menu, it's more often than not referring to a velvety, satiny soup with relatively little to no dairy fat. We start this asparagus/tarragon version by cooking leeks and fennel, vegetable stock, and asparagus, before puréeing it all to a smooth and creamy consistency.
- 2 tablespoons (30ml) extra-virgin olive oil, plus more for serving
- 1 large leek, white and pale green parts only, finely chopped (about 6 ounces; 170g)
- 1 fennel bulb, trimmed and thinly sliced (about 4 ounces; 120g), plus a few fennel fronds for garnish
- Kosher salt
- 2 tablespoons (15g) all-purpose flour
- 4 cups (960ml) homemade or store-bought low-sodium chicken or vegetable stock
- 2 pounds (900g) asparagus, trimmed and cut into 1 1/2–inch lengths
- Small handful minced fresh tarragon leaves, plus more for serving
- 2 tablespoons (30ml) fresh juice from 1 lemon
- Freshly ground black pepper
- Crème fraîche, for serving (optional)
Heat olive oil in a large saucepan over medium-low heat until shimmering. Add leek and fennel and a large pinch of salt. Cook, stirring frequently, until fully softened but not browned, about 5 minutes. Add flour and cook, stirring, until incorporated, about 30 seconds. Stir in stock and bring to a simmer.
Stir in asparagus and tarragon. Bring to a simmer and cook for 1 minute. Using a slotted spoon, remove a dozen asparagus tips from the pot, split them in half lengthwise, and set them aside for garnish. Continue simmering soup for 5 to 6 minutes longer. Stir in lemon juice.
Blend soup using a handheld immersion blender, or in batches using a countertop blender, until it's as smooth as you like. Season soup to taste with salt and pepper and serve, garnishing with reserved asparagus tips, crème fraîche (if using), more chopped tarragon, fennel fronds, and more extra-virgin olive oil.
Countertop blender or hand blender