Begin by rinsing the mixed salad greens thoroughly under cold running water. Pat them dry and place in a large serving bowl.

Gently wash the fresh blueberries in a colander under cool water and allow to drain.

Chop the shelled pistachios roughly to maintain some texture.

In the bowl with the prepared greens, add the rinsed blueberries, chopped pistachios, crumbled feta cheese, and red onion. Toss gently.

In a small bowl, whisk together the olive oil, honey, balsamic vinegar, mustard, salt, and pepper until emulsified.

Drizzle the dressing over the salad and toss gently. Taste and adjust seasoning if necessary.

Serve immediately to enjoy the fresh flavors at their peak.