Thinly slice the onions and cut up the kale. Melt half of the butter in a frying pan over medium-low heat. When its foam has subsided, add the onions plus a pinch of salt and cook until the onions *just* start to brown. Add the greens, stirring them to coat. Add a splash of water, cover the skillet, turn heat to low, and let the greens cook until tender.

Meanwhile, crack the eggs and whisk. Add a good amount of black pepper, a pinch of salt, and all but a fifth or so of the cheese; whisk.

When the greens are ready, turn off heat, and remove the greens from the pan and add them to the egg/cheese mixture. Add the other 2 tablespoons of butter and heat on medium. When you are sure the pan is hot (test), dump the eggs/greens mixture into the pan—there should be an audible sizzle—and immediately turn heat to low. Sprinkle the reserved cheese evenly over the surface and let your frittata cook until the egg mixture sets at the edges all around—run a butter knife around the edges to make sure.

Now turn the broiler on in your oven, where the frittata will finish cooking, and set a rack about 8" from the top of the oven. Place the skillet on the rack under the oven's hot broiler, and let it cook until lighly brown and fully set. It won't take long.

Remove the skillet from the oven and place a cutting board over it—one that's larger than the skillet itself. Carefully—using oven mits on both hands—press the skillet and rack together and invert them them, so that the frittata falls on the cutting board. Serve

http://www.motherjones.com/tom-philpott/2012/03/toms-kitchen-frittata-greens