A good batch of sweet potato marshmallow bars starts with roasted sweet potatoes whipped smooth, then baked under a blanket of melted marshmallows until the top turns golden in spots. This recipe gives you a chewy, lightly spiced base with a soft marshmallow layer that holds its shape when cooled. You get a make-ahead dessert that travels well in a 9×13 pan and slices into neat squares.
The base uses brown sugar and cinnamon so the sweetness reads as warm rather than flat. Because the sweet potato adds moisture, the bars stay tender for days in the fridge. They work as a holiday side or a casual weeknight treat with coffee. If you enjoyed this, our scottish potato scone is worth trying next. Making this sweet potato marshmallow bars at home is surprisingly straightforward once you know the key steps.
Why You’ll Love These Sweet Potato Marshmallow Bars
- Baked in one 9×13 pan with no fussy layering or piping.
- Sweet potato keeps the crumb moist without extra butter.
- Marshmallow top toasts in the last minutes for a campfire note.
- Cuts into 16 clean squares after a short chill.
- Freezes solid for up to two months in a sealed container.
Ingredients You’ll Need
- 2 cups mashed roasted sweet potato (about 2 large potatoes, skin removed)
- 1/2 cup unsalted butter, melted
- 3/4 cup packed brown sugar
- 2 large eggs
- 1 tsp vanilla extract
- 1 cup all-purpose flour
- 1 tsp baking powder
- 1/2 tsp salt
- 1 tsp ground cinnamon
- 3 cups mini marshmallows
The mashed sweet potato should be smooth and cooled so it doesn’t cook the eggs when mixed. Mini marshmallows melt faster and more evenly than large ones, giving you a level top. The sweet potato marshmallow bars works well for weeknight cooking when time is limited.
Ingredient Substitutions
Unsalted butter: Replace with an equal amount of coconut oil for a dairy-free base. Coconut oil firms up more at room temperature, so the bars will feel a little denser and less rich on the tongue. The cinnamon flavor stays the same, but you may notice a faint coconut note in the background. Bake at the same temperature, though the top may brown slightly slower.
All-purpose flour: Swap with an equal weight of oat flour if you want a softer, more tender bite. Oat flour absorbs liquid differently, so let the batter rest for 5 minutes before spreading it in the pan. The crumb will be more cake-like and less structured, which still holds the marshmallow layer fine. Skip this if you need a firm edge for clean lunch-box squares.
Brown sugar: Use an equal amount of maple syrup plus 2 tablespoons less mashed potato to balance moisture. Maple shifts the sweetness toward a woodsy note and deepens the color to a darker amber. The bars will be a touch stickier, so extend the chill time by 30 minutes. Keep the oven temp the same.
Mini marshmallows: Replace with an equal volume of chopped marshmallow creme cubes if you want a smoother top. Creme melts faster and can sink, so press the pieces gently into the batter before baking. You lose the toasted peaks but gain a glossy, uniform surface. Watch the last minutes closely so it doesn’t bubble over.
Step-by-Step Instructions
- Heat the oven to 180°C / 350°F and grease a 9×13 baking pan with butter or line it with parchment.
- Mash the cooled roasted sweet potato until no lumps remain, then stir in the melted butter, brown sugar, eggs, and vanilla until the mix looks like loose pudding.
- Add the flour, baking powder, salt, and cinnamon, folding just until you see no dry streaks. do not overmix or the bars will turn rubbery.
- Spread the batter evenly in the pan and bake for 25–30 minutes until the center springs back and the edges look golden and crispy.
- Remove the pan and scatter the mini marshmallows across the top in a single layer, then return it to the oven for 5 minutes until they puff and show light brown spots.
- Cool on a rack for 20 minutes, then chill in the fridge for up to 3 days or at least 1 hour before cutting into 16 squares.
Pro Tips
Roast the sweet potatoes whole at 200°C / 400°F for 45 minutes so the flesh caramelizes instead of steaming, which builds a deeper flavor in the bars.
Press the marshmallows into a flat layer with the back of a spoon right before the final bake so they melt into an even sheet rather than separate mounds.
Chill the baked pan for a full hour if you want sharp edges; a warm cut will drag the marshmallow and smear the top.
Read about oven calibration if your bars brown too fast, since home ovens often run 10 to 15 degrees off.
Common Mistakes to Avoid
Using hot sweet potato from the oven will start to cook the eggs in the bowl and give you sweet potato marshmallow bars with a curdled base. Cool the mash to room temperature first.
Skipping the chill step leads to torn squares because the marshmallow is still tacky. A short fridge rest sets the top so a knife passes cleanly.
Piling marshmallows too thick means the center stays raw while the top burns. One even layer is enough to cover the surface without overflow.
Serving Suggestions
Cut the cold bars into small squares and plate them with a dusting of cinnamon sugar for a light dessert after roast chicken. They pair well with overnight oats at a brunch table if you want a soft contrast.
For a holiday board, set them next to almond ring cake so guests get a chewy option beside a crisp one. A hot drink like warm spiced toddy balances the sweetness.
Storage and Reheating
Keep the bars in an airtight container in the fridge for up to 3 days, separated by parchment so the tops don’t stick. They freeze solid for freeze for up to 2 months in a sealed tray.
To reheat, warm a square in the microwave for 15 seconds until the marshmallow softens, or bake a tray at 160°C / 325°F for 8 minutes. Don’t leave cut bars out for more than 2 hours since the potato base spoils at room temperature.
Yes, this freezes well for up to 2 months. Thaw overnight in the fridge before serving cold or reheating.
Recipe Variations
Pecan Crunch Version
Stir 1/2 cup chopped toasted pecans into the batter before baking for a nutty bite against the soft marshmallow. The nuts add a dry crunch that contrasts the chewy top, and they brown nicely in the same oven time. Watch the edges so the pecans don’t scorch in the final minutes.
Cranberry Swirl Option
Drop 1/3 cup whole-berry cranberry sauce in small dots over the batter and swirl with a knife before the first bake. The tart berries cut the brown sugar sweetness and give a red marbled look under the marshmallow. Expect a slightly wetter center, so add 5 minutes to the base bake.
Spiced Maple Bars
Replace the vanilla with 1 tablespoon maple extract and add 1/4 teaspoon ground ginger to the dry mix for a warmer profile. The bars taste closer to a fall pie filling with a toasted top. Serve with coffee drink to round out the spice.
Potato Base Swap
Use mashed potato technique to prep riced potato instead of sweet, then follow the same steps for a neutral base. The color will be pale and the flavor milder, letting the marshmallow lead. Add an extra 1/2 teaspoon cinnamon so the bars don’t taste plain.
Mini Muffin Format
Spoon the batter into a greased 24-cup mini muffin tin, bake 15 minutes, then top each with 3 marshmallows and broil 1 minute. You get portable sweet potato marshmallow bars for lunch boxes with the same taste in bite size. Cool fully before popping them out or the tops stick.
Sweet Potato Marshmallow Bars
Description
Roasted sweet potatoes are whipped smooth and baked into a chewy, cinnamon-spiced base under a blanket of melted mini marshmallows. These make-ahead bars travel well in a 9x13 pan and slice into neat squares after a short chill.
Ingredients
Instructions
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Heat and prepare pan
Heat the oven to 180°C / 350°F and grease a 9x13 baking pan with butter or line it with parchment. Make sure the pan is evenly coated so the bars release cleanly after baking and chilling.
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Mix wet ingredients
Mash the cooled roasted sweet potato until no lumps remain, then stir in the melted butter, brown sugar, eggs, and vanilla until the mix looks like loose pudding. Use sweet potato cooled to room temperature so the eggs do not start cooking in the bowl and curdle the base.
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Fold in dry ingredients
Add the flour, baking powder, salt, and cinnamon, folding just until you see no dry streaks. Do not overmix or the bars will turn rubbery from too much gluten development.
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Bake the base
Spread the batter evenly in the pan and bake for 25–30 minutes at 180°C / 350°F until the center springs back when lightly touched and the edges look golden and crispy. Pull the pan when the top is set and a toothpick inserted near the center comes out with a few moist crumbs.
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Add marshmallows
Remove the pan and scatter the mini marshmallows across the top in a single layer, then return it to the oven for 5 minutes until they puff and show light brown spots. Press the marshmallows into a flat layer with the back of a spoon before this final bake so they melt into an even sheet.
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Cool on rack
Cool on a rack for 20 minutes so the surface stops bubbling and the pan is safe to handle. This initial cool prevents the marshmallow from smearing when you move the pan to the fridge.
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Chill before cutting
Chill in the fridge for at least 1 hour (up to 3 days) before cutting into 16 squares with a sharp knife. A full hour chill sets the marshmallow top so the knife passes cleanly without dragging.
Nutrition Facts
Servings 16
- Amount Per Serving
- Calories 220kcal
- % Daily Value *
- Total Fat 7g11%
- Saturated Fat 4g20%
- Cholesterol 35mg12%
- Sodium 160mg7%
- Total Carbohydrate 36g12%
- Dietary Fiber 2g8%
- Sugars 22g
- Protein 3g6%
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.
Note
- Storage: Keep bars in an airtight container in the fridge for up to 3 days, separated by parchment so tops don't stick; discard any left out more than 2 hours.
- Make ahead: Roast sweet potatoes whole at 200°C for 45 minutes to build deeper flavor, as shared in our scottish potato scone post.
- Pro tip: Chill the baked pan for a full hour for sharp edges; a warm cut will drag the marshmallow and smear the top.
- Reheating: Warm a square in the microwave 15 seconds or bake a tray at 160°C for 8 minutes until the marshmallow softens.
