Cheesy Rosemary Mashed Potato Casserole
This Cheesy Rosemary Mashed Potato Casserole may be the best mash you’ll ever eat. This side everything you want from your favorite side dish, creamy, cheesy, full of rosemary flavor with a crispy topping. The best make ahead holiday side dish.

This is recipe #3 in this weeks complete holiday dinner series. In case you missed them, I’ve already published slow cooker green beans with shallots and almonds and the star of the table, herb roasted beef tenderloin.
I don’t really know where to start talking about this casserole. I do know I ate too much of it before I sat down for my meal and I do know that any holiday dinner. Whether it’s Thanksgiving or Christmas, really good mash is mandatory.

A great make ahead dish
This Cheesy Rosemary Mashed Potato Casserole is the perfect dish to take some help from prepping ahead. You can make this a couple of days before your holiday dinner. Make up to the point of baking but don’t add the panko and Parmesan. Cover and refrigerate until ready to bake, add the toppings then as directed in the recipe. How easy was that?
Mash until your arm hurts for no lumps
The key to really soft and creamy mash is first, you have to mash really well. If there are any lumps, well, no mash really should have lumps. I live by my ricer for mashed potatoes. if you haven’t seen a ricer, it’s like a giant garlic press. You can see it in the video below.

Here are the other recipes for the complete holiday dinner that you can see in the picture above:
- Herb Roasted Beef Tenderloin
- Homemade Creamy Horseradish Sauce
- Slow Cooker Green Beans with Shallots and Almonds
If you’ve made this, or any other recipe, leave a comment below. I love to hear from my readers and feedback is very important.
Cheesy Rosemary Mashed Potato Casserole

Mashed potato with fresh rosemary and cheese is soft and creamy. Topped with breadcrumbs and Parmesan then baked.
Ingredients
- 5 pounds (2.2) potatoes of your choice, peeled and quartered
- 2 tablespoons salt
- 2 cups (473 ml) heavy cream, warm
- 1/2 cup (113 grams) unsalted butter, melted
- 1 cup (83 grams) white cheddar cheese, grated
- 1 cup (83 grams) mozzarella cheese, grated
- 2 tablespoons fresh rosemary, chopped
- 1/2 teaspoon ground black pepper
- 1 cup (108 grams) panko breadcrumbs
- 1 cup (83 grams) Parmesan cheese, grated
Instructions
- Add the potatoes to a large pan and cover with water. Bring to a boil, add the 2 tablespoons salt and simmer for 15 minutes until tender. Drain and add to a large bowl.
- Preheat oven to 375°F/190°C. Butter the inside of a 9 x 13-inch (23 x 33 cm) casserole dish.
- Run the potatoes through a ricer or food mill or mash really well to get the smoothest mash possible
- Add the cream, butter, cheeses, rosemary and pepper. Stir until combined and the cheese is melted. Taste and add salt if needed.
- Pour the mash into the casserole dish and spread evenly. Mix the breadcrumbs and Parmesan in a bowl. Sprinkle an even layer of breadcrumbs and Parmesan cheese on top of the mashed potato.
- Bake for 30 minutes until the top is golden.
Nutrition Information
Yield
6Serving Size
1Amount Per Serving Calories 750Saturated Fat 32gCholesterol 172mgSodium 2505mgCarbohydrates 43gProtein 27g
6 Comments on “Cheesy Rosemary Mashed Potato Casserole”
Question: Can it be prepared without the topping, then frozen? I would like to make it a couple of weeks ahead.
This dish is perfect to make ahead. Prepare it up to step 4 then you can either freeze it in the dish you’re going to bake it in, or a container that will fit in your freezer. The day before you’re ready to bake, take it out of the freezer and thaw in the fridge overnight. Make sure you bring it to room temperature before baking (this is important if it is in the baking dish so it is not too cold for a hot oven). This is a good time to prepare the panko topping, then bake per the recipe. Enjoy! Let me know if you have any more questions.
Lovely and creamy mash and the crispy panko topping is perfect. Will make this again for the holidays.
This is one of my favorites
So good. I love the combination of smooth mash with the crunchy topping
Thank you, I’m glad you enjoyed it.