Make the vinaigrette: Combine the vinegar, horseradish, salt, pepper, and mustard in
a small bowl and whisk to combine. Slowly drizzle the oil into the mixture as you whisk vigorously until thoroughly combined. Alternatively, you can throw everything into the blender and put it on high for a few seconds. Set aside.
Place the potatoes in a medium saucepan and cover with cold water by about an inch or two. Bring to a boil over medium-high heat and cook until potatoes yield to a paring knife easily, but not so easily that they mush, about 12 minutes. Remove the
potatoes with a slotted spoon and set aside. Place the beet roots in the boiling water and cook until you achieve the same knife-yielding tenderness of the potatoes. This
should take longer, about 20 minutes. Remove with a slotted spoon, allow to cool slightly, and peel. Cut potatoes and beets into small wedges and set aside in
Peel and pit the avocado. Slice it into 1/4 inch thick pieces and lay onto your serving
plate. Squeeze the lemon over top of the avocado slices and season with salt and
pepper. Drizzle a bit of the dressing here too. Arrange the beets on top of the avocado. Drizzle some of the dressing on top. Sprinkle with salt, pepper and some of
the chives. Arrange the potatoes on top of the beets and drizzle with more dressing, salt, pepper and the remaining chives. Scatter the capers on top. Serve with a dollop
of crème fraiche, if desired.