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Leftover Mashed Potato Lorraine is a savory casserole using leftover mashed potatoes mixed with leeks, bacon, and Swiss cheese.
The last couple of weeks I shared with you two recipes for holiday entertaining, Cheerwine Holiday Punch and Green Bean Casserole. As much as I love recipes for entertaining, I also love recipes for the leftovers.

Having leftover food can be a wonderful thing. It means that at some point in the next few days you won’t have to cook or shop as much. I actually get kind of bummed when I don’t have a lot of leftovers after a holiday meal, especially Thanksgiving. A post-Thanksgiving turkey sandwich is a must for me!
However, too many leftovers can seem quite daunting. Re-eating the same meal over and over again can get boring. Some dishes aren’t always as good the second time around. You have to get a little extra creative when repurposing them. I find that mashed potatoes are one of those dishes.
Leftover mashed potatoes are pretty good when they’re reheated in the oven. This makes them ideal for a potato casserole. I’ve seen quite a few loaded potato casserole recipes that call for mashed potatoes. As much as I love loaded potatoes, I wanted something different.

As I contemplated different ingredients to add to my leftover mashed potatoes there was one that really stood out, leeks. I think it’s because of my affinity for potato leek soup. I knew I couldn’t stop with just leeks. I then thought of Quiche Lorraine and how it usually includes onion to go along with the bacon and gruyere. Since leeks are a type of onion I thought, “Why not?” It’s a bit of a French twist on a loaded baked potato casserole.
It came out beautifully and I love the flavors! The hubs thoroughly enjoyed it and gave it two thumbs up. You will notice that instead of gruyere I used Swiss cheese. I just did that because the Swiss is more accessible and budget-friendly. However, if you want to take the casserole up a notch then,
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Leftover Mashed Potato Lorraine
Ingredients
- 6 cups leftover mashed potatoes
- 2 leeks sliced and cleaned
- 4 slices bacon cooked and crumbled
- 1 ½ cups baby Swiss cheese shredded
- 2 Tbsp Butter
- Salt and pepper
- 2 slices bacon cooked and crumbled for the topping
- ½ cup baby Swiss cheese shredded for the topping
Instructions
- Preheat oven to 375 degrees.
- In a frying pan over medium heat melt the butter. Add the leeks and season with salt and pepper. Cook for 5-10 minutes until soft and caramelized.
- In a mixing bowl with the leftover mashed potatoes, add the leeks, 4 slices of crumbled bacon, and 1 ½ cups shredded Swiss. Mix together thoroughly.
- Add the mixture to a greased 2-quart casserole dish. Top with the reserved Swiss cheese and bacon and bake for 30-45 minutes. Remove from oven and serve.
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