For oven roast: Preheat oven to 375°F. Cut off beet greens, leaving 1-inch stems; leave root intact. Scrub clean with water and place in a glass baking dish. Add water to about ¼ inch, cover tightly with foil, and bake for about 45 minutes, until beets are fork-tender. When cool enough to handle, peel then slice into rounds or cut pole-topole into 8 wedges (or cut some of each).
For sous vide: Trim off the roots and greens, wash and peel the beets. Place the beets in a sous vide bag (I kept the yellow beets separate from the red by using two bags) and drizzle in a tablespoon of olive oil and a teaspoon of wine vinegar. To make a sous vide bag, use FoodSaver vacuum bags, Zip-lock freezer bags, or silicone Stasher bags—just keep in mind that the bag’s color will never be the same after you cook red beets in it. Cook to 185°, which takes about 2 hours for 2-inch beets. Remove from water bath and let cool. Refrigerate until you are ready to make the salad.
Make the dressing by combining the shallots with the vinegars in a glass measuring cup or bowl. Stir in the horseradish, capers, parsley, salt and a few grinds of fresh black pepper.
After the beets are cooked, peel each one and cut into small dice.
How to dice a beet: Cut the roly poly beet in half so you have something stable to work with, instead of a ball. Make horizontal slab slices through each half, stack back up then slice lengthwise, trying to keep your stack together, then cut crossways and you have dice. Transfer to a bowl, drizzle with dressing and stir to combine. Refrigerate at his point up to one week.
Serve with a spoon of crème fraîche, fromage blanc/farmer's cheese, or Greek yogurt. Pairs nicely with sliced radicchio and endive. Drizzle with a little olive oil if you like.