Place a rack in upper third of oven and preheat to 425°. Place 1½ lb. skinless, boneless chicken thighs (about 6), patted dry, in a large bowl. Drizzle 1 Tbsp. extra-virgin olive oil over, season with kosher salt and freshly ground pepper, and toss to coat.

Whisk ¼ cup balsamic vinegar, ¼ cup pomegranate molasses, 3 Tbsp. Worcestershire sauce, and 2 tsp. ground cumin in a small saucepan. Drizzle 3 Tbsp. over chicken; toss to coat. Stir a pinch of salt into remaining sauce in pan; set aside.

Arrange chicken on a rimmed baking sheet and roast until lightly browned, 13–16 minutes. Remove from oven.

Meanwhile, toast 1 cup raw walnuts in a single layer on another rimmed baking sheet, stirring once, until golden brown, 5–8 minutes. Remove from oven.

Set reserved sauce in pan over medium-high heat and cook, stirring occasionally, until thick and syrupy, about 5 minutes.

Heat broiler. Brush chicken with sauce, then broil until cooked through and deeply browned and blistered in spots, about 5 minutes. Remove from heat and brush with more sauce.

Coarsely chop walnuts and transfer to a medium bowl. Add 1 garlic clove, finely grated, ½ tsp. crushed red pepper flakes, ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt, and remaining 5 Tbsp. extra-virgin olive oil and mix to combine walnut relish.

Transfer chicken to a platter and spoon walnut relish over. Scatter 1 large scallion, thinly sliced on a diagonal, ¼ cup (packed) mint leaves, large leaves torn, and some pomegranate seeds on top.