1) Remove the tough outer leaves of the escarole and twist from the core, discard. Wash in a deep bowl filled with very cold water and swish around until all the dirt has rested on the bottom of the bowl. Lift the leaves from the bowl and spin dry in small batches in a salad spinner.
2) Heat the butter, oil and red pepper flakes in a skillet over medium-high heat. Add half of the escarole and stir until just wilted. Add the remaining escarole and cook until softened but still has a little crunch.
Season with the salt and serve.