Tamarind Chicken Thighs With Collard Greens Salad

Name: Tamarind Chicken Thighs With Collard Greens Salad
Ingredients: 8 skin-on, bone-in chicken thighs (about 2½ lb.), patted dry; Kosher salt; 2 serrano chiles, coarsely chopped; 1 2 piece ginger, peeled, chopped; 3 garlic cloves; ⅓ cup tamarind concentrate; 3 Tbsp. coconut aminos; 2 Tbsp. agave nectar; 2 tsp. ground cinnamon; 1 tsp. ground nutmeg; ½ cup plus 3 Tbsp. fresh orange juice (from about 2 oranges); 3 Tbsp. extra-virgin olive oil, divided; 2 medium Japanese sweet potatoes or other sweet potatoes (about 1 lb.), scrubbed, sliced into 1/8–1/4-thick rounds; Half a bunch collard greens (about 6 oz.), stems removed, leaves cut or torn into bite-size pieces; Freshly ground black pepper