Cheesy Mashed Potato Casserole

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Are you looking for a new holiday side dish? or better yet something to do with your leftover mashed potatoes? This Cheesy Mashed Potato Casserole is a little bit like a twice baked potato casserole but healthier than traditional versions that are normally full of bacon and heavy cream. Making a cheesy mashed potato casserole is a great way to use leftover mashed potatoes! This recipe brings your mashed potatoes back to life.

Why You’ll Love This Cheesy Mashed Potato Casserole

Whether you are looking for the perfect holiday side dish or a clever way to repurpose last night’s dinner, this casserole is a game-changer. Here is why it’s about to become a favorite in your kitchen:

• The Ultimate Leftover Makeover: It breathe new life into leftover mashed potatoes, transforming them from a plain side into a rich, flavorful bake.
• Sneaky Nutrition: By folding in frozen collard greens, you’re adding a punch of Southern greens and vitamins without compromising that classic “comfort food” feel.
• Healthier Comfort: It captures the vibe of a twice-baked potato but stays lighter than traditional versions that rely on heavy cream and bacon.
• Effortless Prep: With only 10 minutes of active prep time, you can get this in the oven and get back to your life while it bakes to golden perfection.
• Incredibly Adaptable: It’s naturally vegetarian, but you can easily make it vegan by swapping in your favorite plant milk and dairy-free cheese shreds.

Looking for more to fill your plate? Check out this collection of 20+ Vegetarian Southern Side Dishes for the perfect pairing.

What’s In This Casserole?

It’s a pretty simple recipe that uses your leftover mashed potatoes. This cheesy mashed potato casserole also uses frozen collard greens. What a great way to sneak a green vegtable into your meal. It’s the perfect recipe for using up holiday leftovers but you can make this casserole anytime of year. The active prep cooking time is only ten minutes and then it bakes for forty five minutes. While you move on with your life and do something else. We could all use a little extra time during the holiday season. Repurposing leftovers is a great way to save time and money. Waste not want not and all that.

For this recipe you need:

• 3 cups of mashed potatoes (Skins or no skins? Either is fine!)
• 1 cup of frozen collard greens
• Garlic powder
• Onion powder
• Red pepper flakes
• A little bit of milk. This just brings the mashed potatoes back to life if they have dried out. Plant milk works here if you want to make it vegan. If your are using fresh mashed potatoes, not leftovers, then use a little less milk.
• 1 cup of shredded cheddar cheese. Make it vegan by using dairy free shreds.

Frequently Asked Questions

Can I use fresh potatoes instead of leftovers?

Absolutely! If you aren’t using leftover mashed potatoes, just whip up a fresh batch. Pro Tip: Use slightly less milk in the casserole mix if your potatoes are fresh and already creamy, as leftover potatoes tend to dry out and absorb more liquid.

Do I have to use collard greens?

Not at all. While frozen collard greens provide that classic Southern flair and great texture, you can easily swap them for frozen chopped spinach. Just make sure to squeeze out any excess moisture before mixing them in.

How do I make this recipe vegan?

It is very simple to adapt! Replace the cow’s milk with an unsweetened plant milk (like oat or soy) and swap the cheddar for your favorite dairy-free cheese shreds. Since the potatoes are the base, it still turns out incredibly creamy.

Can I prep this casserole in advance?

Yes! You can assemble the entire casserole (up until the baking step), cover it tightly, and keep it in the fridge for up to 24 hours. When you’re ready to eat, just pop it in the oven. You may need to add 5–10 minutes to the bake time if it’s going in cold from the refrigerator.

What is the best way to reheat leftovers?

To keep the potatoes from drying out, reheat portions in the oven at 350°F covered with foil until warmed through. If you’re in a hurry, the microwave works too. Just mix in a tiny splash of milk before heating to restore the creaminess.

Looking for other casserole ideas?

Try one of these Breakfast Casseroles! Our Everything Bagel Vegetarian Breakfast Casserole is perfect for your next brunch because all the work is done the night before so all you have to do in the morning is pop it in the oven. If that doesn’t do it for you maybe check out our Easy Vegetarian Breakfast Casserole.

Looking for a vegan potato casserole? Try our Vegan Potato and Collard Greens Casserole.