Carbonara Mashed Potatoes

Preheat the oven to 425°. Brush the bottom and sides of a 9-by-13-inch or 3-quart baking dish with 2 tbsp. butter. Place the potatoes in a large pot and cover with cold salted water by 2 inches. Bring to a boil over high heat and cook until they can easily be pierced with a fork, about 15 minutes. Drain and return to the pot.

Meanwhile, cook the bacon in a small nonstick skillet over medium heat until crispy, stirring occasionally, 6 to 7 minutes. Use a slotted spoon to remove the bacon to a paper towel–lined plate. Reserve 3 tbsp. of bacon fat. In a medium bowl, whisk the heavy cream, Parmesan, whole eggs and yolks, 1 tsp. black pepper, nutmeg, and several generous pinches of salt.

Add the reserved bacon fat and 10 tbsp. butter to the pot with the potatoes and mash until the butter has melted. While mashing, use a ladle or small measuring cup to pour a third of the egg mixture into the potatoes and mash until well combined. Repeat 2 more times, mashing until the potatoes are smooth and creamy. (Adding the eggs in batches while mashing prevents scrambling.)

Stir in the cooked bacon and transfer the mixture to the prepared baking dish. Use the back of a spoon to create swirls in the top of the potatoes. Dot with the remaining 4 tbsp. butter and sprinkle with the remaining 1/4 tsp. black pepper. Bake until puffy and golden brown, about 30 minutes. Let rest for 10 minutes before serving.