Wash the beetroots thoroughly.
Boil or roast the beetroots until tender, about 30-40 minutes.
Let the beetroots cool, then peel them.
Slice the beetroots into thin rounds or wedges.
In a large bowl, combine the mixed salad greens.
Add the sliced beetroots to the greens.
Sprinkle the crumbled feta cheese over the salad.
Add the chopped walnuts for crunch.
Drizzle with olive oil and balsamic vinegar.
Season with salt and pepper to taste, then toss gently.