Irish Baked Mashed Potato Casserole

01Method

1. 1

   Heat the oven to 400°F on the convection setting if your oven has one. Grease the bottom and sides of a 1½ to 2-quart casserole dish with 1 tablespoon of the butter and set it aside.

2. 2

   Place the potatoes and garlic clove in a large pot and cover generously with cold salted water. Bring to a boil over high heat, then lower to medium-high and cook until a fork slides in easily, 15 to 20 minutes. Drain in a colander and let the potatoes steam-dry for 10 minutes.

3. 3

   While the potatoes dry, melt the remaining butter in the same pot over medium heat. Add the green onions and cook, stirring, until softened and fragrant, about 1 minute. Take the pot off the heat.

4. 4

   Press the potatoes and garlic through a ricer or food mill directly into the pot, discarding the skins. If using a masher, peel the skins by hand, then mash the potatoes in the pot until smooth. Fold everything together with a spatula until evenly combined.

5. 5

   Incorporate the milk into the potato mixture in three additions, folding gently each time. The mixture will be quite loose but will firm up during baking. Stir in half of the nutmeg and the cayenne, then season with salt and pepper. Transfer the mixture to the prepared dish and scatter the cheese evenly over the surface.

6. 6

   Bake until the potatoes have puffed slightly and the cheese is melted and golden in spots, about 30 minutes. If your oven lacks a convection setting, broil for 1 to 3 minutes to brown the top. Dust the remaining nutmeg over the finished casserole and serve right away. Leftovers keep covered in the refrigerator for up to 5 days; reheat in the microwave until piping hot.