Step 1

Boil the unpeeled potatoes. Slice the squash and steam it. In a pan, sauté the spinach with a tablespoon of oil and a pinch of salt, letting it wilt. Peel the potatoes, mash them, and let them cool.

Step 2

Mash the squash with a fork. Break up the chestnuts with your fingers. Add the chestnuts, the chopped spinach, 2 tablespoons of the mashed potatoes, and a pinch of salt to the squash.

Step 3

To the remaining potatoes, add the egg yolks, some freshly grated nutmeg, and 2 heaping tablespoons of cheese; combine well.

Step 4

Spread the potato mixture onto a wide sheet of parchment paper, leveling it out to form a 1/8-inch thick layer. Spread the squash mixture on top and use the parchment paper to help you roll it up.

Step 5

Close up the roll in the parchment paper, and then again with a sheet of aluminum foil; place it in the freezer for 2-3 hours: this will make it firm and easier to slice (you can also prepare this the day before and keep it in the fridge; in this case, you won’t need to place it in the freezer). Cut 16 slices about 3/4-inch thick and dust them with bread crumbs. Add butter and a handful of sage to a pan; once the butter begins to foam, toast the slices until they are golden on both sides.