Roasted Garlic Cheddar Soup

whole heads garlic

extra-virgin olive oil, divided

large leek, sliced and washed and drained

chopped fresh thyme leaves

kosher salt

dry white wine

reduced sodium chicken broth or stock or vegetarian no-chicken broth

thin-skinned waxy potatoes, such as Yukon gold, peeled and cut into 1-inch chunks

-ounces extra-sharp cheddar cheese, shredded (1 cup)

plain Greek yogurt

scallions, sliced