This gratin is likely to become a new tradition for your holiday table. Cubes of bright orange pumpkin and creamy white potato are blended with smoky bacon and a spiced egg custard. The gratin is topped with a generous handful of nutty Gruyere and crisp Japanese breadcrumbs, which creates a toasty brown crust. This gratin tastes fantastic and looks like a photograph in a fancy food magazine.
6 cups peeled and cubed (1-inch) fresh pumpkin (about 1 ½ pounds)
2 large russet potatoes, peeled and cut into 1-inch cubes
salt to taste
½ stick unsalted butter (4 tablespoons), brought to room temperature, divided
½ teaspoon freshly grated nutmeg
2 teaspoons finely chopped fresh sage
Freshly ground black pepper, to taste
3 large eggs
1 ½ cups shredded Gruyere cheese (6 ounces), divided
8 slices smoked bacon, cooked until crisp, cooled and crumbled (reserve rendered bacon fat)
1 medium red onion, diced
1 cup Japanese breadcrumbs (panko)
1 green onion, green tops only, very thinly sliced
1. Preheat oven to 400 degrees. Place the pumpkin and potato cubes in a medium sauce pan with enough cold water to cover. Add a large pinch of salt, and bring to the boil. Immediately reduce the heat to a simmer, and cook, uncovered, until the potatoes are tender when pierced with the tip of a small knife, about 20 minutes. Drain in a colander, then return to the same pan (off the heat).
2. Add 3 tablespoons full of the butter to the pan, and mash with a potato masher (or pass through a food mill). Add the nutmeg and sage, then season to taste with salt and pepper. Whisk in the eggs, one at a time, until completely combined, then stir in half the cheese.
3. Heat a medium sauté pan over medium heat; add 1 to 2 tablespoonfuls of the reserved bacon fat and heat through. Stir in the onion, and cook until tender and translucent, about 5-8 minutes.
4. Oil the bottom of a 2-quart gratin dish with some of the reserved bacon fat. Layer the sautéed onions on the bottom oft the oiled pan. Spread the pumpkin mixture evenly over the onions, then sprinkle the remaining cheese evenly over the top/
5. Blend the remaining tablespoonful of butter with the breadcrumbs, green onion and crumbled bacon; sprinkle evenly over the cheese mixture.
6. Bake, uncovered, until the crust is light golden brown, about 30-45 minutes. If the crust is getting too grown, cover with aluminum foil to finish the cooking process; let stand 10 minutes before serving.
Substitute acorn or butternut squash for the pumpkin.
Make it ahead: assemble the gratin through step 5 up to two days in advance, remove from the refrigerator 30 minutes before baking.