Acorn and Butternut Squash Gratin Casserole

This Acorn and Butternut Squash Gratin Casserole is made “Provencal style” with two types of winters squashes, whole roasted garlic, chunks of potatoes and tons of Gruyere cheese, which creates the most amazing topping. This is hands-down the best Thanksgiving vegetable side dish you could put on your table. 

Similar to this Potato Leek Casserole this winter squash gratin dish is rich and decadent and will complement any meal.

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The inspiration for this Acorn and Butternut Squash Gratin Recipe

A few years ago I came across a “The New Classic Cookbook” by Saveur.  It contains thousands of recipes from around the world. Some are classic recipes typical to a specific region, and some are recipes with a twist or adjustments with the ingredients that can be easily found in the US.

I remember stumbling upon this Squash Gratin recipe and I decided to give it a try. Originally it comes from the Provence region of France, and is intended to be made from the French pumpkin, called “potiron.” However, this pumpkin is difficult to find outside of Europe and therefore a combination of acorn squash with butternut squash can be substituted to achieve a similar texture and taste.

I tried this recipe a few times and my husband really liked it, but I felt like some adjustments were needed. So, here is my take on this Provencal squash gratin. I hope you’ll like it as much as we do.

Unique Texture in Acorn and Butternut Squash Gratin Casserole

This Acorn and Butternut Squash Gratin is not your typical casserole; the texture is completely different and surprising. Your squash isn’t sliced into chunks but is boiled first and then roughly mashed with a potato masher.

And the differences don’t end there. It’s then mixed with parboiled chunky potatoes. Then mixed with an amazing meddle of roasted garlic, sauteed onions and dried thyme. Essentially this makes for a texture that is creamy and chunky at the same time, with some sweet notes from both the garlic and onions and an earthiness with fall flavor from dried thyme.

And then for the most pleasant surprise… Milk is poured over the entire mixture and lots of freshly shredded Gruyere cheese is sprinkled over to create an irresistible crust on top.

I’m convinced that this dish is going to be the topic conversation at your Thanksgiving table. It’s beyond delicious and is simply unforgettable. Try sneaking this dish onto your table, with little fanfare, and let me know if I was right. By the way, if you’re interested in other Thanksgiving ideas, make sure to check this post for My Favorite Thanksgiving Recipes.

What Ingredients are Needed to Make this Squash Casserole?

So, the ingredients list is simple and all products can be purchased in your local grocery store. Nothing fancy (maybe Gruyere is a bit fancy, but it’s found in every grocery store). Here’s your list:

• Large Acorn Squash, whole or pre-cut;
• Large Butternut Squash, whole or pre-cut (I like pre-cut squashes, especially for a dish like this, when I can simply put the chunks in the water and boil. But if you can’t find it then just go for the whole one);
• 3-4 Russets, or Yellow Potatoes;
• Whole Garlic Clove, roasted to perfection;
• Sweet Onion;
• Dry Thyme;
• Milk;
• Gruyere Cheese,
• Salt, Pepper, and Fresh Nutmeg.

Once you’ve gathered all your ingredients, you are ready to make this squash gratin casserole!

This is not intended to replace the recipe itself. I just want to show you what you’ll need to gather in order to make this recipe. Scroll down to the recipe card for exact measurements, instructions, and nutritional information.

How to Make Acorn This Casserole

Here are simple steps on how to make this casserole (check out the photos below to see these steps).

Step 1: Roast your garlic. Peel the paper off the garlic head, then cut off the top of the head and place it in a tin foil. Sprinkle with olive oil, salt & pepper, and roast at 400F for 40 minutes. You can see very good instructions on how to do this on TheKitchn website – I often use their Instructables. They’re so easy to follow. Once your garlic is roasted, keep the oven hot at 400F;

Step 2: Peel and cut your squash (unless you purchased pre-cut then skip this step). In order to make it easier to peel, cut the squash in half and then place it into a microwave for 2 minutes. Let cool before peeling. Then peel and cut into about 1-inch squares. You may want to check my Ulitmate Guide to Winter Squashes for all tips and tricks on how to buy, store, peel and cook them;

Step 3: Place both squashes into a large pot with salted water and bring to boil. Reduce to a simmer and partially cover. Cook squashes until fork-tender, for about 20 minutes;

Step 4: Peel the potatoes and slice them into 1/4 inch thick slices. Place potatoes in a pot of salted water, bring to boil, then reduce to a simmer, and finally cover and cook until tender, for about 10 minutes;

Step 5: Chop your onions. Then heat up a skillet, add some olive oil, your onions, and dry thyme. Sprinkle with some salt & pepper and cook until onions are soft and translucent (for approx 5 minutes). Then squeeze out the cloves from the roasted garlic head and add them to the pan. Mash the garlic cloves using a wooden spoon and mix all together;

Step 6: Drain your squashes in a colander and place back into a large bowl. Using a potato masher, roughly mash the squashes;

Step 7: Add onions, thyme and garlic mixture into the bowl. Then add salt, pepper, fresh nutmeg and mix everything gently. Check for seasoning and adjust as needed;

Step 8: Once potatoes are fork-tender, drain them and to the bowl with squashes;

Step 9: Transfer the squash mixture into a 9 x 13″ baking dish,

Step 10: Pour milk over the squash mixture;

Step 11: Shred your Gruyere cheese and place it on top of the milk;

Step 12: Transfer the baking dish into the oven and bake for 30 minutes, until bubbly and golden brown;

Step 13: Remove from the oven and let cool slightly before serving.

This section is meant to visually show you how to make this delicious casserole recipe. For exact instructions scroll down to a recipe card.

What to Serve this Casserole With

If you want to serve this Acorn and Butternut Squash Gratin Casserole for your Thanksgiving or Christmas, here are some other suggestions of what to serve it with:

• Fall Harvest Roasted Turkey Breast
• Slow Cooker Turkey Breast
• Maple Mustard Glazed Turkey
• Brown Sugar Pork Loin with Garlic and Herbs

For other occasions or simple weekend meal, you can serve it alongside:

• Oven Roasted Chicken Leggs
• Olive Oil Chicken Thighs
• Chicken Provencal with Shallots and Garlic
• Slow Cooker Whole Roasted Chicken

What Equipment is Needed to Make this Winter Gratin?

You may already have most of these items in your kitchen, but I wanted to list them here to make sure that you have everything needed to make this awesome casserole.

• Large Pot (or two) for boiling squashes and potatoes;
• Colander;
• Potato Masher;
• Large Mixing Bowl;
• Set of Knives;
• Cutting Board;
• 9×13″ Casserole Dish;
• Cheese Grater.

Other Squash Recipes to Try

• Roasted Butternut Squash Feta Pierogi
• Butternut Squash Beef Stew with Cinnamon and Pomegranates
• Turkey Stuffed Acorn Squash
• Lentils Stuffed Acorn Squash
• Truffled Butternut Squash Mushroom Soup

Acorn and Butternut Squash Gratin Casserole

This Acorn and Butternut Squash Gratin Casserole is made "Provencal style" with two types of winters squashes, whole roasted garlic, chunks of potatoes and tons of Gruyere cheese that creates the most amazing topping. This is the best Thanksgiving vegetable side dish you could put on your table. 

4.28 from 11 votes

Print Pin Rate

Course: Casserole, Side Dish

Cuisine: French

Prep Time: 20 minutes minutes

Cook Time: 50 minutes minutes

Roasting Garlic: 1 hour hour

Total Time: 1 hour hour 10 minutes minutes

Servings: 8

Calories: 382kcal

Author: Edyta

Ingredients

• 1 Large Acorn Squash Peeled and cut in 1 inch cubes
• 1 Large Butternut Squash Peeled and cut in 1 inch cubes
• 4 Medium Yellow Potatoes Thickly sliced
• 1 whole Roasted garlic
• 1/2 Large Sweet Onions Chopped
• 1/2 teaspoon Dry Thyme
• 1/2 teaspoon Fresh Nutmeg
• 1 cup Milk Whole or 2 %
• 3 cups Gruyere Cheese Shredded (about 0.5 lbs)
• 1 tbsp Olive Oil for cooking onions

Instructions

• Roast your garlic. Peel the paper off the garlic head; Chop the top of your garlic head and place the whole head in a tin foil, sprinkle with olive oil, salt and pepper, and roast at 400F for an hour.  Once your garlic is roasted, remove it from the oven and let it cool off. Keep the oven hot at 400F.
• Peel and cut your squash (unless you purchased pre-cut then skip this step). In order to make it easier to peel, cut the squash in half, place in a microwave for 2 minutes; let cool before peeling; then peel and cut into about 1-inch squares; 
• Place both squashes into a large pot with salted water and bring to boil; reduce to simmer and partially cover; cook squashes until fork-tender for about 20 minutes;
• Peel the potatoes and sliced them in 1/4 inch thick slices; place potatoes in a pot of salted water, bring to boil, then reduce to simmer, cover and cook until tender for about 10 minutes;
• Chop your onions, heat up a skillet, add some olive oil, onions and dry tyme; sprinkle with some salt and pepper and cook until onions are soft and translucent (for approx, 5 minutes); Squeeze out garlic cloves from the roasted garlic head and add them to the onions; break the garlic using wooden spoon and mix all together;
• Drain your squashes in a colander and place back into a large bowl. Using a potato masher, roughly mash the squashes;
• Add onions, thyme and garlic mixture into the bowl; add salt, pepper, fresh nutmeg and mix everything gently; check for seasoning and adjust as needed;
• Once potatoes are fork-tender, drain them and to the bowl with squashes;
• Transfer the squashes mixture into a 9x13 baking dish,
• Pour milk over the squashes mixture;
• Step 11: Shred your Gruyere cheese and place it on top of the milk;
• Transfer the baking dish into the preheated oven to 400F and bake for 30 minutes until bubbly and golden brown;
•  Remove from the oven and let cool slightly before serving.

Nutrition

Calories: 382kcal | Carbohydrates: 37g | Protein: 19g | Fat: 18g | Saturated Fat: 10g | Cholesterol: 56mg | Sodium: 196mg | Potassium: 1225mg | Fiber: 6g | Sugar: 4g | Vitamin A: 12970IU | Vitamin C: 46mg | Calcium: 653mg | Iron: 4.4mg

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This post was originally published on November 1, 2018.

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