Prepare the Vinaigrette: In a small bowl or a glass jar with a lid, combine the white balsamic vinegar, olive oil, Dijon mustard, and honey. Whisk vigorously or shake the jar until the dressing is well-emulsified and creamy. Season with salt and pepper to your liking. Set aside.

Toast the Pecans: Place the pecans in a dry skillet over medium heat. Toast for 3-5 minutes, shaking the pan frequently, until they are fragrant and slightly browned. Remove from heat and set aside to cool.

Assemble the Salad: In a large salad bowl, combine the mixed greens, sliced peaches, fresh blueberries, and thinly sliced red onion.

Dress and Toss: Drizzle about half of the prepared vinaigrette over the salad and gently toss to coat the ingredients evenly.

Add Toppings and Serve: Just before serving, sprinkle the crumbled feta cheese and toasted pecans over the top. Garnish with fresh mint leaves, if desired. Serve immediately with the remaining dressing on the side.