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Root Vegetable Gratin
- 6 Tbsp unsalted butter
- 4 cups finely sliced onions
- 4 lbs. Yukon gold potatoes, peeled
- 1 lb. winter squash, sweet potato, etc.
- salt and pepper to taste
- Preheat oven to 400 degrees F. Add butter and onions to a large pot and slowly sweat the onions until they’re tender, without any browning. While the onions are sweating, slice potatoes to about 1 to 2 mm thick into large bowl. Add potatoes to the onions and mix until all the potatoes are coated with the butter and onions.
Lightly pepper the mixture and add salt until you can just taste the saltiness over the sweetness of the onion
- Line the bottom of a 10-inch cast iron skillet or heavy bottomed baking dish with parchment paper and place potatoes so that it’s heaping full. Once full, cut another piece of parchment to cover the top, wrap the whole with aluminum foil, and bake on a sheet tray for 1 3/4 to 2 hours, uncovering for the last ten minutes. It’s ready when you can pierce the potatoes through with a skewer and feel no resistance.
- Remove pan from oven and let cool at room temperature for about 45 minutes, then gently press down on top of the potatoes until the top is flat. Cool in the refrigerator to meld the flavors for 5 or 6 hours. Overnight works best.