A big winner with the kids, and the grownups liked it too. I like to use penne with macaroni and cheese for some reason, but feel free to use the traditional elbows.
1/2 lb kale, stemmed
3 Tbsp butter
3 Tbsp white flour
2 1/2 cups milk, warmed
1 lb cut pasta, such as penne or rotini
8 ounces shredded sharp cheddar
Salt and pepper to taste
Either chop the kale very finely or pulse it briefly in a food processor until finely chopped but not totally pureed. Set aside.
Begin by making a classic white sauce: Melt the butter in a heavy saucepan or deep skillet, then stir in the flour. Keeping the heat very low, whisk it constantly as it browns and thickens, bubbling. Slowly whisk in the milk a little at a time, over low heat. Whisk constantly until the sauce thickens a bit, then raise the heat to medium until the sauce reaches a simmer. Turn the heat down again at that point and cook for about 10 minutes, stirring frequently (you can switch to a spoon for this).
While the white sauce cooks, boil the pasta in a large pot of salted water.
After the sauce has simmered for its 10 minutes, stir in the kale and let simmer for another minute or two. Then remove sauce from the heat and stir in the cheese, a handful or so at a time, until it melts. Taste and add salt and pepper.
When the pasta is done, drain it and return it to the pot. Pour the sauce over it and stir to coat evenly. Serve hot.