Step 1Heat the oven to 350 degrees. Place the red and golden beets in two separate sealed foil packets and roast until tender, about 45 to 60 minutes. Once the beets are cool enough to handle, peel them. Cut the beets into wedges, keeping the two colors separate.
Step 2Whisk together the olive oil, sherry vinegar, chives and shallots and season to taste with salt and white pepper. Separately marinate the beets with the vinaigrette.
Step 1Clean the endives and cut off the bottom inch of each. Slice off the stem, then thinly slice the cut-off end of each endive. Carefully separate the remaining leaves, wrap in wet paper towels and chill.
Step 1Whisk together the vinegar and mustard and slowly drizzle in the walnut and olive oils until emulsified. Stir in the shallot and season to taste with salt and white pepper.
Step 1Juice the beet in a juicer or puree in a blender. Place the juice or puree in a cheesecloth-lined strainer and strain or squeeze out the juice.
Step 2Place the juice in a small saucepan over medium heat, reduce to a syrup and set aside.
Step 1Place the walnuts and butter in a small baking dish and roast in a 350-degree oven until golden brown, about 15 to 20 minutes. Drain on paper towels and season with salt.
Step 1Sprinkle the walnut vinaigrette onto the endive leaves and the sliced endive and gently toss to coat. Season to taste with salt and pepper. Repeat with the beet greens or mustard greens, if using.
Step 2Alternate 3 wedges of red beets with 2 wedges of yellow beets in the center of each of 6 serving plates. Arrange 4 of the red endive leaves so the tips are pointing up, leaning on the beet wedges, and 4 of the yellow leaves pointing to the left, placed below the wedges on each plate. Crumble the blue cheese and divide among the 6 serving plates. Scatter 5 walnut halves around each plate with the torn beet greens. Drizzle the beet reduction over and around the salad and serve.