Prep the cabbage: Remove any damaged outer leaves. Cut the cabbage into quarters, remove the core, and finely shred.
Massage with salt: Place the cabbage in a large bowl. Sprinkle the salt over it and begin massaging with your hands until it softens and starts releasing liquid — about 5–10 minutes.
Toast the spices: In a dry skillet, toast cumin and fenugreek seeds over medium heat for 1–2 minutes, until fragrant. Be careful not to burn them. Let cool slightly.
Add flavor: Mix the toasted spices (and optional garlic or chili) into the cabbage. Toss well.
Pack the jar: Transfer everything into a clean glass jar or fermentation crock. Press it down firmly — the liquid should rise and cover the cabbage. If needed, place a small weight (like a clean glass or fermentation weight) on top.
Cover and ferment: Cover loosely with a lid or cloth. Leave at room temperature (not too warm, around 18–22°C / 65–72°F) for 3–5 days.
Taste and store: After a few days, start tasting. When it’s tangy enough for your liking, seal the jar and refrigerate. The flavor will continue to develop slowly in the fridge.