In a small saucepan bring kale stems, water, sea salt, mustard & coriander seeds, chili flakes, and peppercorns to a boil.

Once boiled, remove from heat and cover with saucepan lid. Let sit for about 20-45 minutes until room temperature. If you have especially tough stems, you may want to low boil for about 2-3 minutes before removing from the heat.

When mixture is room temp add apple cider vinegar & maple syrup and stir to combine.

Pour mixture into a sterilized (you can boil it and then rinse in vinegar water) 500ml mason jar. Cover top of jar with parchment paper then seal with lid.

Let sit in warm place out of direct sunlight for at least 1 week. You can leave it for up to 4 weeks before moving to the fridge.

Refrigerate once open and always use a clean utensil when removing stems from the jar to consume.