Make Ahead Tips
The onions can be made up to 3 days in advance. Transfer them to a bowl, cover with plastic, and refrigerate. The gratin can be baked up to 1 day ahead to the point of adding the breadcrumb topping. Reheat at 375°F until bubbling and hot throughout, about 20 minutes, and then add the topping and bake 10 minutes more.
Not sure how to use a mandoline? Check out our instructional video.
Used a mandolin which made this so much easier to prep and make ahead. Delicious flavors! Take your time with the onions. Also, I used the “white” sweet potatoes, not orange yams. Would be good either way. I used more parmigiano than called for and I bought it from our local cheese shop, so it was very fresh. I served this alongside beef tenderloin, but wouldn’t hesitate making this for Thanksgiving.
This has become a mainstay at my Thanksgiving dinners. I particularly like the "make ahead" aspect of the dish, I make this the day before and it keeps well. Give it a go, the recipe works well!
I liked this recipie and the overall taste - my only complaint is that my carmelized onions clumped together after cooking and it was very difficult to sprinkle them evently in the layers as directed. Some bites had no onion despite my best effors while other had too much.
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