In 5-quart Dutch oven, heat oil over medium-high heat. Cook onions in oil 2 to 3 minutes or until translucent, stirring frequently. Stir in garlic. Cook 1 minute. Add potatoes; mix until potatoes are covered with oil. Stir in broth, milk, salt and pepper. Heat to boiling. Cover; reduce heat to medium. Simmer 17 to 22 minutes or until toothpick inserted in potato comes out easily.