Beans and Green Soup with Salted Yogurt and Sizzled Mint

Name: Beans and Green Soup with Salted Yogurt and Sizzled Mint
Ingredients: 3 tablespoons vegetable oil; 1 large onion, finely chopped; 3 garlic cloves, finely grated; ½ cup cranberry or navy beans, soaked overnight, drained; ½ cup dried chickpeas, soaked overnight, drained; 1 teaspoon ground turmeric; ½ cup green lentils, rinsed; 5 ounces baby spinach (about 7 cups), chopped; 1 cup chopped cilantro leaves with tender stems; 1 cup chopped parsley; ½ cup chopped dill; 2 tablespoons fresh lemon juice; Kosher salt; freshly ground pepper; 6 tablespoons vegetable oil, divided; 1 large onion, very thinly sliced; ⅓ cup whole-milk Greek yogurt; ¼ cup buttermilk; Kosher salt; 2 tablespoons dried ground mint