Put your pasta on to cook while you prepare the kale. Separate kale leaves from large stems. (If you’re using red russian kale, you might need to discard the toughest bits at the ends of the stems.) Wash the stems and leaves, dry, keep separate. Chop the stems finely, tear the leaves roughly, and set both aside.
In a large pan, heat the olive oil and butter and add the chopped stems. Cook on medium heat for 1-2 mins. Add the garlic and chilli flakes and cook, stirring, for another minute. Add the kale leaves, salt and pepper and continue to sauté until the kale has wilted and softened – about 4-7 minutes, depending on type of kale. Turn the heat off.
Add the hot drained pasta to the kale pot and mix together. If using egg, mix this in now. If no egg, you might want to add a glug of extra virgin olive oil. Finally, mix the parmesan in, reserving some to sprinkle on when serving.