Cover your scrubbed (and potentially peelepotatoes with enough water to boil them, in a large soup sized pot (so you can use it throughout the entire process.) Cook them for 20-30 minutes, until they are cooked all the way through, but still firm. Dutch Creams were a dream for this.
Remove the potatoes from the water, and allow them to steam dry. Ideally (if you have timallow them to cool – it will make slicing them much easier.
When your potatoes are ready, cut them into reasonably thin slices – as you would for scalloped potatoes. Set aside, and preheat the oven to 180 degrees Celsius.
Crack your pepper. Unless you’re bougie (which I fully supporand have a powered pepper grinder, this will take a while. Worth it, trust me.
Have all your other ingredients ready to go – grate the pecorino, weigh the butter, measure out the cornflour, and grab your whisk. You could also measure out the milk, but I like to have one cup measure filled and ready, and just use that to add the remaining 3 cups. Saves on dishes.
Place the soup pot on a medium heat, emptying it if it’s filled with water. Allow the bottom of it to dry completely, before adding the cracked pepper. Allow it to cook just until it becomes fragrant, and then add the butter.
Once the butter has melted and mingled with the pepper, add the cornflour, and quickly whisk it until they’re combined and beginning to bubble. Once they are, add the milk, and whisk to remove any lumps.
Cook this mixture for about 10 minutes, until it is reasonably thick and could easily coat the back of a spoon. A thin custard type thickness is ideal. Once it is ready, add the finely grated pecorino, and stir intermittently until it has completely melted.
Take the roux off the heat, and add the sliced potatoes. It helps if you separate the slices with your hands beforehand, so they get evenly coated in the sauce.
Stir the potatoes and sauce gently until the potatoes are completely covered. I like to use a spatula to do this, so I can scrape all the sauce out at the end.
Carefully pour the mixture into a large baking dish. Mine is 31cm x 23cm, and 5cm deep. If the mixture is cool enough, I like to use my hands to flatten all the slices down. This helps squeeze up some sauce from the bottom, and ensures all the potatoes cook evenly. If you’re not a grub like I am, you could use the spatula.
Sprinkle the remaining grated cheese over the bake, and then pop in the oven for 30-50 minutes. Once the top is beautifully browned you can remove it from the oven and serve.
As I mentioned, I serve mine with a lightly dressed radicchio salad, but you do you.