Instant Pot® Cottage Pie Soup
Feel free to substitute lamb for the beef to make this a shepherd's pie soup. It even works great with venison, making it a hunter's pie soup.
Short on time and don't have any leftover mashed potatoes? You can use a 4-ounce package of instant mashed potatoes prepared according to package directions instead. After mixing them, stick them in the refrigerator for 10 minutes to cool before adding the egg yolk and brushing with butter.