Bake beets for 1 hour in a 400 oven, after you've taken off the greens and washed the beets. Cool them. Peel them (paper towels do this job nicely.) Refrigerate them. This part is best gone a day ahead. Whisk vinegar and olive oil with garlic and sugar. Add S&P to taste. In a large bowl, mix the greens, onions and beets. Pour the dressing over them. Divide into 6 plates. Crumble cheese and walnuts over the top and serve.