8 medium beets, trimmed, greens reserved
7 to 8 tablespoons water
1 large russet potato, peeled, cut into 1 1/2-inch pieces

1/2 cup walnuts, toasted, cooled
1/2 cup fresh breadcrumbs made from crustless French bread
3 tablespoons fresh lemon juice
5 garlic cloves
1/4 cup plus 2 tablespoons extra-virgin olive oil

2 tablespoons red wine vinegar
2 tablespoons drained capers

Cook beets in large pot of boiling salted water until tender when pierced with skewer, about 30 minutes. Drain. Cool slightly. Peel and cut beets into 1/4- to 1/2-inch-thick slices; set aside. Combine beet greens and 3 tablespoons water in large skillet. Cover and cook over medium-high heat until greens are wilted, about 1 minute; set aside. Cook potato in small saucepan of boiling salted water until tender, about 15 minutes. Drain. Return to saucepan and mash.

Blend walnuts, breadcrumbs, 2 tablespoons lemon juice, garlic, and 2 tablespoons water in processor until smooth. Transfer to bowl. Mix in 1/2 cup mashed potato, 1/4 cup olive oil, and 1 tablespoon lemon juice. Season with salt and pepper. If thick, thin sauce with 2 to 3 tablespoons water.

Spoon sauce onto center of platter; drizzle with 2 tablespoons oil. Surround with beet greens and beet slices; drizzle with vinegar. Sprinkle with capers.