Begin by rinsing the cabbage and discarding any wilted outer leaves. Quarter the cabbage using a sharp knife and remove the core. Slice the cabbage into thin strips, about ¼ inch wide. It doesn’t need to be perfectly even. If you prefer, you can also use shredded cabbage. Transfer the sliced cabbage into a large bowl and sprinkle the sea salt evenly over it.

Take a handful of the mashed cabbage and place it into a clean glass jar. Press it down firmly with a wooden spoon to remove any air bubbles. Keep packing and pressing the cabbage in small batches until the jar is almost full, leaving about 1 to 2 inches of space at the top.

If the cabbage isn’t fully covered in its own liquid, make a simple 2% brine by dissolving 1 tablespoon of fine sea salt in 4 cups of non-chlorinated water. Pour the brine over the cabbage until everything is submerged. Any extra brine can be stored in the fridge for later use.

Cover the cabbage with the brine, leaving about 2 inches of space from the top. If the cabbage floats, use a glass weight or wedge a piece of the cabbage core on top to keep it down. Seal the jar loosely with a linen cloth or a similar cover and secure it with a rubber band.

Place the jar in a dark spot at room temperature, away from direct sunlight, for at least one week. To prevent spills, place a small dish or tray under the jar since it might leak slightly during fermentation.

Open the lid after a day or so to release any built-up gas. After one week, taste and smell your sauerkraut. If it’s tangy enough for your taste, move it to the refrigerator. If you like it sharper and more sour, let it ferment a few days longer.

Enjoy your sauerkraut as a side dish, in stir fries, or in a warm Polish-style sauerkraut soup.