Step 1: In a dry skillet over medium heat, gently toast the walnuts for 3-4 minutes until fragrant. Watch them closely so they do not burn. Let them cool.
Step 2: In a small bowl, whisk the olive oil, apple cider vinegar, Dijon mustard, salt, and black pepper together until completely emulsified.
Step 3: Place your fresh organic mixed greens into a large serving bowl. Arrange the thin apple slices and cooled toasted walnuts beautifully over the top.
Step 4: Drizzle the vinaigrette evenly across the salad, toss gently, and scatter the crumbled feta cheese over the top right before serving.