Heat a drizzle of oil in a large frying pan on medium heat. Cook bacon for a few minutes or until starting to turn crispy. Set aside.
Add onion to bacon fat and cook for a few minutes until soft, then add garlic and thyme, and continue cooking for 2 minutes more. Add chopped kale and continue cooking for a few minutes until kale has wilted.
Preheat oven to 200°C. Grease a medium-large baking dish with butter. Roughly layer one third of the potato slices over the base of the dish (slightly overlapping) and season with a little salt and pepper. Spoon over half the kale mixture and sprinkle over half the bacon. Arrange half of remaining potato slices on top and season with salt and pepper. Add remaining kale mixture and then the bacon. Finally, top with the last layer of potato slices.
Pour over cream. Season with salt and pepper. Cover with foil and bake for 45 minutes or until potato is almost tender. Remove foil, sprinkle over cheese and bake for a further 20-30 minutes until potatoes are cooked all the way through and cheese is golden and bubbling. Allow to stand for 10-15 minutes before serving.