Remove any damaged outer leaves. Halve the head lengthwise through the stem, then cut each half into quarters. Cut out and discard the tough core from each quarter. Thinly slice crosswise into strips — thin shreds cook faster and more evenly; slightly thicker cuts hold more texture. If using onion or garlic, slice and mince them now before the pan gets hot. Keep a small cup of water nearby in case the cabbage dries out during cooking.

Heat a large skillet over medium to medium-high heat. Add butter, olive oil, or both and let it heat through. If using onion, cook 3–4 minutes until translucent. Add garlic and cook 30 seconds — keep it moving, it burns fast. Add shredded cabbage, toss to coat. The pan will look overfull; it wilts down. Cook over medium to medium-high heat, stirring every 1–2 minutes, for 10–16 minutes. If cabbage sticks or dries out before it's tender, add a small splash of water. For softer cabbage, add water early, cover, and reduce heat to low for part of the cook — still stir frequently. Season with salt and pepper during cooking. Add sugar or red pepper flakes early so they distribute evenly.

Cabbage is done when tender and lightly browned in spots — soft with slightly crisp, caramelized edges. For softer results, cook a few more minutes. For more crispness, add a drizzle of oil once water has evaporated and cook uncovered 1–2 more minutes. Finish with a small splash of apple cider vinegar in the last minute and stir well. Serve hot. Leftovers keep 3–5 days refrigerated in a covered container.