Preheat the oven to 425 degrees. Place a rack in a roasting pan or on a baking sheet.
Rinse the chicken in cold water; pat dry. In a wide bowl or on a plate, season the flour with salt and 1/4 teaspoon pepper. Dredge each chicken piece through the flour so it's fully coated, tap against the bowl to shake off excess flour and set aside. Discard the flour.
Here comes the part kids like best: Crush the cornflakes by placing them in a big resealable plastic bag, carefully pressing the bag to push out the air. Seal up the bag (with as little air inside as possible) and run over the flakes with a rolling pin. Open the bag and pour the crushed flakes into a wide bowl or onto a plate.
In a large bowl (big enough to dredge the chicken pieces), mix the buttermilk, mustard, cayenne pepper, paprika and sage. Give each floured chicken piece a good buttermilk bath and then roll in the cornflake crumbs.
Arrange the chicken pieces on the rack and place in the hot oven. Cook for 15 to 20 minutes, lower the heat to 375 degrees and cook for another 25 to 30 minutes, until cooked through and crispy. The juices should run clear when the meat is pierced with a knife. Serve with Easy Greens.