Step 1

Preheat oven to 350°. Toast pistachios on a rimmed baking sheet, tossing occasionally, until fragrant but not browned, 5–8 minutes. Let cool.

Step 2

Cook fava beans in a large saucepan of boiling salted water until tender, about 4 minutes. Using a slotted spoon, transfer to a colander set in a bowl of ice water. Drain, remove skins, and transfer beans to a small bowl.

Step 3

Combine shallot and vinegar in another small bowl; season with salt and pepper and set aside at least 10 minutes. Whisk oil into shallot mixture; season vinaigrette with salt and pepper.

Step 4

Combine beans, asparagus, watercress, mint, and tarragon in a large bowl; add vinaigrette and pistachios and toss to combine. Transfer to a serving platter and top with chive blossoms, if using.