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Take some of the stress out of your Thanksgiving meal with this Make-ahead Sweet Potato Casserole! A rich, creamy sweet potato base is topped with either mini marshmallows or a buttery, crunchy pecan streusel — or, you could go half-and-half and top the casserole with both to keep both team marshmallow and team streusel happy!
See recipe card below for full list of measurements, ingredients, and instructions.
Why This Is The Only Sweet Potato Casserole Recipe You’ll Ever Need!
- This is everything you want in a sweet potato casserole for Thanksgiving: a light, rich and creamy sweet potato layer is topped with either a sweet, crunchy, nutty streusel or classic marshmallows. You could even make a casserole with half streusel and half marshmallows to keep everyone around the table happy — no need to choose!
- I’ve specifically written this casserole recipe so that you can make it ahead, either just the sweet potato part, or the streusel too. You can even freeze it up to a month ahead (instructions below!) All you need to to is assemble and bake!
- I’ve also written this recipe to make it flexible. Cook the sweet potatoes any which way (I’ve tried it and all methods work, suggestions below!) and to use either heavy cream or milk so you can use up whichever carton you’ve got open in the fridge for other recipes.
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What I Learned Testing This Recipe
- Make sure you drain the sweet potatoes really well before adding any heavy cream or milk. Not doing this step properly is usually how I’ve ended up with a watery casserole in the past!
- Don’t be tempted to chill the casserole fully assembled. When I tried each topping version both toppings ended up wet and soggy as the streusel absorbed liquid from the sweet potato layer, and the marshmallows did the same and started to melt, but not in a good way!
- Keep a close eye on the marshmallows in case your oven runs hot! They can turn from pleasantly browned and puffy to browned in just seconds. As ovens vary so much, I never trust the recipe times for this, even though I’ve tested the toppings to try and make them as accurate as possible!
Ingredients
Sweet potatoes – We’re peeling, cubing, cooking and mashing the potatoes here, but honestly any cooking method you prefer will work, from the Instant Pot or slow cooker to your air fryer or microwave!
Unsalted butter – Melted to go in the sweet potato layer, and more for the pecan topping cold from the fridge if you’re not making the marshmallow-topped version.
Brown sugar – For both the sweet potato layer, and more for the pecan topping if you’re going that way.
Heavy cream or whole milk – Heavy cream will make a thicker, richer casserole; milk will lighten it up a little! Evaporated milk would also work for a super-rich casserole.
Large eggs – These are an essential binder in any sweet potato casserole, they’re the difference between a spoon-able dish and a sloppy mess!
Vanilla extract – I love adding a dash of vanilla to the sweet potato layer for that signature holiday flavor!
Cinnamon – This adds a touch of spice to both the sweet potato, and the streusel topping if you’re making it.
Salt – Usually I don’t need to explain salt in an ingredient list, but it is essential not to leave it out of your casserole as it is what balances the sweetness in an already sweet dish.
Streusel Topping Option
All-purpose flour – This is essential for keeping the topping together and helping to make it crunchy alongside the nuts. For a gluten-free version you could substitute a 1:1 gluten-free flour blend.
Chopped pecans – Obviously pecans are the quintessential Thanksgiving choice, but topped walnuts would also work.
Marshmallow Topping Option
Mini marshmallows – I always top my Thanksgiving casseroles with mini marshmallows, they just don’t puff up and melt in the same way if you chop bigger ones.
Extra Make-ahead, Leftovers and Storage Tips
While it is best to add the marshmallows just before baking, you can freeze the sweet potato base for up to 1 month. Just make sure you thaw it overnight in the refrigerator first, and bring it up to room temperature before baking.
You can also freeze the streusel topping, unbaked simply freeze it also for up to 1 month in an airtight container or freezer bag. Thaw it in the refrigerator before using, keeping it cold until the moment you’re ready to scatter it over the casserole!
Any leftover casserole after the big meal can be kept in the refrigerator for 3-4 days and re-heated in the microwave (marshmallow version) or in the oven (streusel version, to keep the topping crispy!)
Frequently Asked Questions
Yes, although fresh sweet potatoes will always give the best flavour and texture. Drain them thoroughly before mashing and try to avoid sweetened or syrup-packed varieties as these will add additional sugar to the casserole, which will likely make it excessively sweet.
For best results yes, but if you really are pressed for time and countertop space, I find an additional 5-10 minutes in the oven should do the trick. For the marshmallow version, add this on at the beginning of cooking before adding the marshmallow layer. For the streusel, just keep an eye on it towards the end of cooking, and cover the casserole with foil if it looks like things are getting a little too brown.
Yes! You see I’ve got two different casseroles in these pictures? That is because I doubled the base! However, bake it in two dishes rather than one larger one to keep the cooking times accurate. And if you’re feeding that many people, two casseroles will make things easier to serve at the table, even if they both have the same topping.
Making changes to a recipe can result in recipe failure. Any substitutions or variations listed are simple changes that I believe will work in this recipe, but results are not guaranteed.
Make-Ahead Sweet Potato Casserole
Equipment
- 9×13 baking dish
Ingredients
Sweet Potato Base
- 4 pounds sweet potatoes about 5-6 large, peeled and cubed
- ½ cup unsalted butter melted
- ½ cup brown sugar
- ½ cup heavy cream or whole milk
- 2 large eggs
- 1 teaspoon vanilla extract
- 1 teaspoon cinnamon
- ½ teaspoon salt
Streusel Topping
- 1 cup all-purpose flour
- 1 cup chopped pecans
- ¾ cup brown sugar
- ½ cup unsalted butter cold and cubed
- ½ teaspoon cinnamon
- ¼ teaspoon salt
Marshmallow Topping
- 3 cups mini marshmallows
Instructions
- Boil the sweet potatoes in a large pot of salted water until fork-tender, about 15 to 20 minutes. Drain well and mash until smooth, or use a hand mixer for a silkier texture.
- Beat in the melted butter, brown sugar, cream, eggs, vanilla, cinnamon, and salt until fully combined. Spread the mixture into a greased 9×13 baking dish.
- For the streusel: Combine the flour, pecans, brown sugar, cinnamon, and salt in a bowl. Cut in the cold butter with your fingers or a pastry cutter until the mixture looks like coarse, clumpy sand. Store this in a separate airtight container in the fridge — don't put it on the casserole yet or it will turn soggy!
- To make ahead: Cover the sweet potato base tightly and refrigerate for up to 2 days, or freeze for up to a month (thaw overnight in the fridge before baking). Keep the streusel refrigerated separately the whole time so it stays crumbly instead of soaking into the potatoes.
- To bake: Preheat the oven to 350°F. If the base was frozen, let it come fully to room temperature first. For the streusel version, scatter the topping evenly over the casserole and bake for 30 to 35 minutes, until the topping is golden and the edges are bubbling. For the marshmallow version, bake the casserole uncovered for 20 minutes first, then scatter the mini marshmallows over the top and bake another 8 to 10 minutes, until melted and lightly browned — watch closely, they go from perfect to burnt fast.If you want to split the batch and do half streusel, half marshmallow, that works too — just use a dish with a natural divider or eyeball the halfway line before topping.
Approximate Information for One Serving
Nutrition Disclaimers
Number of total servings shown is approximate. Actual number of servings will depend on your preferred portion sizes.
Nutritional values shown are general guidelines and reflect information for 1 serving using the ingredients listed, not including any optional ingredients. Actual macros may vary slightly depending on specific brands and types of ingredients used.
To determine the weight of one serving, prepare the recipe as instructed. Weigh the finished recipe, then divide the weight of the finished recipe (not including the weight of the container the food is in) by the desired number of servings. Result will be the weight of one serving.
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