I saute in bacon fat with garlic, salt, pepper... or if the leaves are really big it is great in soups like bacon/potato soup. I saute the kale then cook it in the soup until it is very tender and soft.
Even tough grass fed beef cooks faster than grain fed. An example is a chuck roast. My roasts are around 3-4 pounds and grain fed I used to cook for 4 hours at 275 degree oven. Grass fed I can cook to falling apart tender in 3 hours or less!