How to Make It
Preheat the oven to 350°. Spread the beets in a baking dish. Add 1/2 cup of water and cover with foil. Roast for 1 1/2 hours until tender. Let cool, then peel the beets and cut into wedges and slices. Transfer to a bowl.
Meanwhile, spread the brioche cubes on a baking sheet and toast for about 8 minutes, until the cubes are golden.
In a blender, combine the pistachios with 3/4 cup of water and blend at high speed for 1 minute. Strain the sauce into a small bowl and refrigerate until chilled. (It will thicken slightly as it chills.) Season the sauce with salt and pepper.
In a small bowl, whisk the olive oil with the pistachio oil and balsamic vinegar. Season with salt and pepper. Toss 3 tablespoons of the vinaigrette with the beets. Spoon the pistachio sauce onto plates. Mound the beets in the center and top with the sorrel. Drizzle the remaining vinaigrette all around and garnish with the brioche croutons. Serve right away.
Red ribbon sorrel is available from chefsgarden.com.