Slow-Cooker Sheperd's Pie

I saw this recipe a few weeks ago on Melissa's Bargain Blog and thought we'd give it a try. I had all the ingredients in my pantry all ready and sheperd's pie is one of those things that there are so many variations of that I'm always up to try a new one. This one offers the classic flavor of a traditional sheperd's pie, but it cooks in the slow cooker all day...LOVE that!

1 pound ground beef, browned and drained
(I added 1/2 onion, diced and some minced garlic)
1 can (10 ¾ ounces) tomato soup, condensed
1 can (15 oz) whole kernel corn, drained
1 can (15 oz) French cut green beans, drained
½ tsp. basil
2 cups instant mashed potatoes, prepared (I made 3 cups mashed potatoes from potatoes we had on hand)
2 cups grated cheddar cheese

In a separate bowl, combine beef, tomato soup, corn, beans, and basil. Pour mixture in the bottom of a greased 3 ½ to 5 quart slow cooker. Spread mashed potatoes on top. Cover and cook on low heat 5-6 hours. The last hour of cooking, sprinkle cheese on top of potatoes.