Wash and trim the asparagus spears. Blanch them in boiling salted water for 2-3 minutes, until tender but still crisp. Drain and rinse with cold water. In a large bowl, whisk together olive oil, lemon juice, Dijon mustard, salt, and pepper. Add the blanched asparagus, crumbled feta cheese, and chopped fresh herbs, such as mint or basil. Toss to combine. Serve chilled.
