01 -
Place diced potatoes in a large pot of cold salted water. Bring to a gentle boil and cook until fork-tender, about 15 to 20 minutes. Drain and let cool completely to maintain shape.
02 -
Preheat oven to 400°F. Wrap each beet tightly in foil and roast for approximately 40 minutes until easily pierced with a knife. Allow to cool, then peel by rubbing skins off under running water and dice into small cubes.
03 -
In a large bowl, whisk together olive oil, balsamic vinegar, Dijon mustard, salt, and freshly ground black pepper until thick and glossy.
04 -
Add cooled potatoes and diced roasted beets to the dressing. Gently fold with a spatula to evenly coat without mashing the potatoes or bleeding beet color.
05 -
Arrange fresh arugula or spinach on serving plates if desired. Spoon the salad mixture over the greens and sprinkle with crumbled feta cheese. Serve chilled or at room temperature.