A quick sauté renders baby kale leaves perfectly tender, allowing them to almost melt into the buttermilk-enriched béchamel in chef and cookbook author Alexander Smalls' riff on mac and cheese. For a smooth sauce, make sure all of the dairy is at room temperature.
8 ounces uncooked cavatelli pasta or other small shell-shaped pasta
1/4 cup plus 2 teaspoons kosher salt, divided
1 tablespoon extra-virgin olive oil
5 ounces baby kale (about 5 cups)
1 teaspoon black pepper, divided
3 tablespoons unsalted butter
3 tablespoons all-purpose flour
1 cup whole milk
1 cup heavy cream
1 cup buttermilk
8 ounces mild cheddar cheese, shredded (about 2 cups)
8 ounces sharp cheddar cheese, shredded (about 2 cups), divided
2 large eggs, beaten
Cook pasta according to package directions, adding 1/4 cup salt to boiling water. Drain; set aside.
Preheat oven to 350°F. Heat oil in a large (12-inch) ovenproof skillet over medium. Add kale by handfuls, stirring to wilt in between additions. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Place kale on a paper towel–lined plate to drain. Wipe skillet clean.
Melt butter in skillet over medium. Add flour, and cook, whisking constantly, until mixture is very lightly browned, 1 to 2 minutes. Gradually add milk and cream, whisking to combine. Add buttermilk, whisking constantly, until completely incorporated. Cook over medium, whisking constantly, until mixture is smooth, thickened, and gently bubbling, 3 to 5 minutes. Remove from heat, and gradually whisk in mild cheddar and 1 cup sharp cheddar until melted and smooth. Whisk in eggs; fold in cooked pasta and drained kale. Season with remaining 1 1/2 teaspoons salt and remaining 3/4 teaspoon pepper. Sprinkle evenly with remaining sharp cheddar.
Bake in preheated oven until lightly brown and bubbling around the edges, 20 to 25 minutes. If desired, broil 1 to 2 minutes to brown the top. Let cool 10 minutes before serving.
