Spiced Chicken with Chickpeas and Spinach

Name: Spiced Chicken with Chickpeas and Spinach
Ingredients: 1 tablespoon vegetable oil; 6 bone-in chicken legs (thigh and drumstick), skin removed; Kosher salt; 1 tablespoon unsalted butter; 2 large onions, thinly sliced; 4 garlic cloves, chopped; 1 1/2 tablespoons grated peeled ginger; 2 teaspoons ground coriander; 2 teaspoons ground cumin; 2 teaspoons ground turmeric; 1/4 teaspoon cayenne pepper; 1 15-ounce can chickpeas, rinsed; 2 cups (or more) low-sodium chicken broth; 5 ounces baby spinach (about 8 lightly packed cups); 1/4 cup Greek yogurt; 1/4 cup fresh cilantro leaves with tender stems