1 1/2 teaspoons olive oil
1 1/2 teaspoons butter
1/2 white onion, chopped
1 cup chopped fresh cilantro, divided
3 cups chopped fresh mushrooms
1/2 teaspoon salt
1/2 teaspoon ground black pepper
6 cups chicken broth
5 cups chopped endive
2 cups milk
1/2 teaspoon cayenne pepper, or to taste
2 cups plain yogurt