1 bunch small red or yellow beets, with their tops attached (about 1 1/2 pounds)
1 cup farro
4 tablespoons extra-virgin olive oil, divided
2 tablespoons finely chopped shallots (about 1 medium)
1 tablespoon plus 1 1/2 teaspoons sherry vinegar
2 teaspoons Dijon mustard
1 1/2 teaspoons honey
1/4 kosher salt, plus more as needed
1/4 teaspoon freshly ground black pepper, plus more as needed
1 cup crumbled feta cheese
Roast the beets: Arrange a rack in the middle of the oven and heat to 375°F. Cut the leafy tops from the beets and set aside. Rinse the beets, then place them on a sheet of aluminum foil. Wrap tightly to completely cover and place on a baking sheet.
Roast until knife-tender, about 1 to 1 1/2 hours. Transfer to a wire rack, unwrap, and set aside to cool. While the beets are roasting, prepare the farro, dressing, and beet greens.
Cook the farro: Bring a large saucepan of heavily salted water to a boil over medium-high heat. Add the farro, reduce the heat to medium, and cook, stirring occasionally, until tender, about 20 to 30 minutes.
Make the dressing: Place 3 tablespoons of the olive oil, shallots, vinegar, mustard, honey, 1/4 teaspoon salt, and 1/4 teaspoon pepper in a large bowl and whisk to combine; set aside.
Sauté the beet greens: Wash the reserved beet greens, dry, and cut crosswise into thin 1/4-inch pieces; set aside. Heat the remaining 1 tablespoon of oil in a large frying pan over medium-high heat until shimmering. Add the beet greens, season with salt and pepper, and cook, stirring occasionally, until wilted and tender, about 4 minutes. Remove the pan from the heat and set aside.
When the farro is ready, drain well in a colander. Re-whisk the dressing, add the hot farro to the bowl, and stir to combine. Let sit until the beets are ready.
When the beets are cool enough to handle, peel and cut them into medium dice. Transfer to the bowl with the farro, add the reserved beet greens and feta, and stir to combine. Taste and season with salt and pepper as needed. Serve warm or at room temperature. Store for up to 3 days in an airtight container in the refrigerator.