1/4 cup all-purpose flour

2 cups whole milk

3 bunches kale (about 1 1/2 pounds), roughly chopped

1/2 cup plus 2 tablespoons grated Parmigiano-Reggiano

1/2 teaspoon freshly grated nutmeg

Freshly ground black pepper

Bring 8 quarts water to a boil and add 2 tablespoons salt. Set up an ice bath in a large bowl.

Preheat the oven to 375 F. Butter a 9-inch round gratin dish.

In a heavy, medium saucepan, melt the butter over medium heat. Add the onion and cloves and cook until golden brown, about 10 minutes.

Add the flour and stir until light golden brown, about 7 minutes.

Gradually whisk in the milk and cook until the mixture boils and thickens, about 10 minutes.

Reduce the heat to low and simmer, whisking frequently, for 5 minutes more. Remove the cloves.

Add the kale to the boiling water and cook until just wilted and tender, about 2 minutes. Drain the kale and transfer to the ice bath to cool for 5 minutes, and then drain well.

Roll up the cooked kale in a kitchen towel or cheesecloth and squeeze out as much liquid as possible.

Finely chop the cooked kale, and then add it to the warm sauce. Add 1/2 cup of the Parmigiano and the nutmeg, season with salt and pepper, and mix well.

Pour the mixture into the buttered gratin dish, top with the remaining 2 tablespoons Parmigiano, and bake for 30 minutes, until bubbly.

(Mario Batali is the award-winning chef behind twenty-four restaurants including Eataly, DelPosto, and his flagship Greenwich Village enoteca, Babbo.)