Cheesy Potato Gratin

Preheat the oven to 200 °C/400 °F.
Slice the potatoes, using a mandoline or a very sharp chef's knife, into 1/8"/ 3-4 mm thick.
In a large bowl, grate the cheddar and Parmesan. Add spices, fresh thyme leaves, cream, milk and melted butter. Stir to combine. Then add potato slices and toss with your hands until every slice is coated with the cream-cheese mixture. Make sure to separate any slices that are sticking together to get the mixture in between every slice.
Grease a baking dish with olive oil. Pick up a handful of potatoes, arrange the slices upright, against each other, until all potatoes have been added. If necessary, slice more potatoes. Pour excess cream-cheese mixture over the potatoes. Cover with aluminum foil and transfer to the oven. Bake for 60 minutes or until tender and cooked through.
After this, remove the aluminum foil. Sprinkle with extra black pepper, crushed red pepper flakes and sage leaves. Return to the oven. Bake until deep golden brown and crispy on top, about 30 minutes.
Remove from oven, let rest for 10 minutes, serve. Enjoy!