How Will I Use the Leftovers? (Shepherd's Pie)

Considering that I only cook for two people, but I make enough to feed 6 to 8 at each meal, we ate a lot of leftovers in this house.  Lunch is always leftovers from the night before, and we have a leftover night on Thursday.  After Thursday everything is finished, frozen, or thrown away.  Last week I had some leftover roast beef.  I considered slicing it up for sandwiches, but there really wasn't enough.  I stuck it in the freezer and waited for inspiration.  That's when I thought of Shepherd's Pie.  If you've never had it, Shepherd's Pie is meat, vegetables and gravy, topped with mashed potatoes and baked.  It's extremely easy to make especially if you have leftover potatoes and vegetables.  All I had was the roast in its juices, but this was still very easy to pull together.  

Here's what I did:

First I made a batch of mashed potatoes.  I made sure to make these like I always do with plenty of garlic and salt.  Each layer should be able to stand alone, so don't skimp on the seasonings.  While the potatoes were boiling, I separated the meat from the broth.  The meat was shredded, and the broth was put on the stove to boil.  I chopped one stalk of celery and one large carrot and added these to the broth.  I let the carrot and celery cook until tender.  Next, I added a 16oz bag of frozen peas to the broth.  Once the broth came back to a boil and boiled for about 5 minutes, I added a few tablespoons of corn starch, whisking while it was added.  When the vegetable/broth mixture was thickened to a gravy, I checked for seasoning and added the beef.  This was placed into a baking dish and topped with the mashed potatoes.  Finally, I sprinkled the potatoes with cheese.  The cheese is optional, and once again, it was a leftover that I needed to use.  I baked the dish at 375 for 20 minutes.