Can leftover mashed potatoes really stand in for butter on grilled cheese? I tested the viral trick to see what actually happens in the pan.
In my house, leftover mashed potatoes are usually either repurposed into buttery fried potato cakes or gnocchi, or they’re simply reheated for dinner and served with a generous ladleful of gravy. But a recent Instagram hack proposed a bolder destiny for everyone’s favorite side: using them to make a grilled cheese sandwich even better.
The idea is to spread mashed potatoes directly onto the outside of the bread, pressing them into the surface before frying the sandwich in olive oil. The result, according to the internet, is a grilled cheese with a crisp exterior and a soft, melty center.
I have a longstanding affection for both grilled cheese and mashed potatoes, which made the idea of putting them together feel like a stroke of genius. I was genuinely giddy to try it. But improving on a sandwich that already feels close to perfect—even with something as magical as mashed potatoes—is a tall order.
How to Make a Grilled Cheese with Leftover Mashed Potatoes
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Start by building and seasoning your sandwich as you normally would. Add your cheese of choice between two slices of bread; something sturdy is key here. Sourdough, country white or thick-cut sandwich breads will hold up better than soft, flimsy slices.
Next, take cold mashed potatoes and spread a generous layer on the outside of each slice of bread. Use the back of a spoon or a spatula to press the potatoes into the surface, evenly coating it and filling in any cracks. You’re aiming for a perfectly smooth layer and full coverage.
Heat a skillet over medium-high heat (slightly higher than you would normally use for grilled cheese) and add a drizzle of oil. Place the sandwich in the pan and cook it until the potato coating turns golden brown, then flip and cook the other side. Higher heat is the key to browning the potatoes so they develop a golden texture.
Once both sides are crisp and the cheese inside is fully melted, remove the sandwich from the pan, then slice and serve it.
Does it taste different from classic grilled cheese?
While this trick didn’t change the sandwich as dramatically as I anticipated, it did make it noticeably heartier—perfect for the cold, rainy afternoon I made it. You don’t exactly taste mashed potatoes in the finished sandwich because they meld so seamlessly into the bread. The flavor stays firmly in grilled cheese territory, with just a faint, french fry–adjacent savoriness at the edges. I noticed the most change in the texture. Where I spread the potatoes a little thicker, there was a soft, pillowy layer beneath the crisp exterior, and that was delightful.
This isn’t an everyday grilled cheese that you whip up when there’s nothing else in the house, but it is a fun twist for when you’re craving something a bit more indulgent and unexpected.
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