Easy Shepherd's Pie

ground beef

medium onion (chopped (roughly 1/2 cup))

garlic clove (crushed or minced)

tomato paste (one 6-ounce can)

Worcestershire sauce

beef broth

frozen mixed vegetables (or about two 10 oz. packages frozen vegetable medley, thawed (carrots, peas, corn, and green beans))

white or russet potatoes (peeled and cut into about 1 inch chunks)

Greek yogurt or sour cream

milk

kosher salt

shredded cheddar cheese (divided)