Thinly slice the cabbage, and put it in a large bowl.
Remove the tough center stem from the collard leaves and thinly slice them. Add them to the bowl.
Prepare the jalapeño pepper: if you want more heat, leave the inner membrane and seeds intact. For a milder flavor, remove the inner white membrane and seeds. Remember not to touch your face or any other sensitive bits until you wash your hands. Add to the bowl.
Mix all the veggies in a large bowl and sprinkle with the salt. Use your hands to squeeze and crush down the veggies until they are slightly wilted.
Load into two pint-sized Mason jars, packing down the veggies firmly.
Once all the veggies are loaded, if the liquid doesn’t completely cover them, mix 1 cup of water with 1 teaspoon of salt in a cup and pour enough in the jar to cover the veggies. You may want to find a small jar to weight down the veggies (if using wide-mouth Mason jars, a 4 oz. jelly jar will fit).
Leave uncapped and cover with a kitchen towel. Keep in a dark cabinet for 1-2 weeks. Check on the liquid level every 1-2 days and top it off if it’s dropped with more salt water (1 cup water : 1 teaspoon salt).
It’s done when the veggies have reached a tart flavor that’s pleasing to your palate – usually 7-14 days depending on climate. Some folks let their sauerkraut ferment far longer. It’s really up to you!