Step 1

Place a rack in upper third of oven; preheat to 350°. Toast walnuts on a rimmed baking sheet, tossing once, until golden brown, 5–8 minutes. Let cool, then coarsely chop. Increase oven temperature to 450°.

Step 2

Toss walnuts, pomegranate seeds, olives, oil, mint, parsley, pomegranate molasses, and garlic in a medium bowl to combine. Season with salt and pepper.

Step 3

Combine rice, butter, and salt in a 13x9" baking dish, then pour in a scant 3½ cups water; top with mint sprigs. Cover tightly with foil and bake until rice is tender and water is absorbed, 30–35 minutes. Remove from oven; pluck out mint. Fluff rice with a fork.

Step 4

Heat broiler. Arrange feta over rice. Broil until rice around edges of pan is browned and crisp and feta is starting to brown, 8–10 minutes. Spoon pomegranate relish over.