Cut the cabbage into quarters and remove the core. Slice the leaves into ribbons about ½ inch wide.
Bring a large pot of salted water to a boil. Add the cabbage and cook for 5–6 minutes, until just tender. Reserve up to ½ cup of the cooking water, then drain the cabbage well and gently press out excess moisture.
Melt the butter in a large skillet over medium-low heat. Add the garlic and cook for 1–2 minutes, stirring often, until fragrant but not browned.
Add the cream and ¼ cup of the reserved cooking water. Bring to a gentle simmer and cook for 4–5 minutes, stirring, until slightly thickened.
Add the cabbage, lemon zest, nutmeg, black pepper, and a small pinch of salt. Toss and simmer for 2–3 minutes, until hot and coated in sauce.
Remove the skillet from the heat. Stir in ¾ cup of the Parmesan, a little at a time. Top with the remaining Parmesan and serve warm. If the sauce is too thick, loosen it with reserved cooking water, one tablespoon at a time.