Set the oven to 400F.
Remove the root of the cabbage and boil its leaves in slightly salted water for about 3 to 5 minutes. Turn off the heat and let the leaves loosen up.
Put a saucepan or skillet over a medium heat setting and add butter. Fry the cauliflower and onion in it. Add salt and pepper as per your taste and then allow it to cool.
Remove the cauliflower-onion mixture in a bowl and add heavy whipping cream, salt, and ground black pepper to it. Pour a chunk of this mixture in the middle of each cabbage leaf, fold around the edges, and make a roll.
In the same skillet or saucepan, fry the rolls on both sides. Keep frying until the rolls turn slightly brownish.
Place the cabbage rolls in a microwave-safe bowl or dish and bake for about 30 minutes. Do not drain the cabbage juice. Just set it aside. We need it for preparing the gravy.
In the skillet or saucepan, add heavy whipping cream, soy sauce, some salt, little pepper, and cabbage juice. Bring the mixture to a boil and then keep boiling for another 5 minutes or so, until it thickens.
Have the Keto cabbage rolls with the gravy.