Heat oven to 400ºF (204ºC) with racks set in upper-middle position and lower-middle position.

Wrap beets individually in foil then place directly on upper-middle oven rack. Roast until a thin knife blade slides into beets with little resistance, 1—2 hours*.

Add walnuts to a sheet pan and transfer to lower-middle oven rack; toast until fragrant and golden brown, 8–12 minutes. Set aside to cool.

Transfer beets to a sheet pan or cutting board and let cool until cool enough to unwrap. Allow beets to cool for about 15 minutes before peeling.*

In a large mixing bowl, combine olive oil, vinegar, mustard and honey. Using a microplane, grate 6 walnut halves into vinaigrette; whisk to combine then season with salt and pepper to taste.

Cut peeled beets into quarters then slice crosswise into ¼-inch thick slices.

Add beets to vinaigrette and toss to coat.

Roughly chop remaining walnuts. Add half of chopped walnuts, half of crumbled feta and half of parsley to salad and toss to combine. Season to taste with salt and pepper.

Transfer salad to a serving bowl or platter and top with remaining walnuts, feta and parsley.