01 - Line a baking sheet with parchment paper. In a small skillet over medium heat, combine walnuts, sugar, water, and a pinch of salt. Stir frequently until the sugar melts and coats the walnuts evenly, approximately 3 to 4 minutes. Spread the candied walnuts on the prepared baking sheet in a single layer to cool completely.
02 - In a small bowl or jar, combine olive oil, balsamic vinegar, honey, Dijon mustard, salt, and pepper. Whisk vigorously until fully emulsified and well combined. Set aside until ready to dress the salad.
03 - In a large salad bowl, combine the baby spinach, sliced strawberries, and thinly sliced red onion. Drizzle the prepared balsamic vinaigrette over the salad mixture and toss gently to coat all ingredients evenly without bruising the spinach.
04 - Sprinkle the crumbled feta cheese and cooled candied walnuts over the dressed salad. Serve immediately to maintain the crisp texture of the spinach and the crunch of the walnuts.