Wash the mixed greens thoroughly and pat dry.
Slice the ripe peaches into wedges, removing the pit.
In a large bowl, combine the mixed greens and peach slices.
Add the crumbled feta cheese to the bowl.
Toast the walnuts in a dry skillet over medium heat until golden brown.
Sprinkle the toasted walnuts over the salad.
In a small bowl, whisk together the olive oil and balsamic vinegar.
Drizzle the dressing over the salad and toss gently to combine.
Season with salt and pepper to taste.
Garnish with fresh mint leaves before serving.