Lay your bacon out onto a parchment lined sheet pan and place in your cold oven. Heat the oven to 375ºF and, once the oven is heated, set a timer for 10 minutes. Check the bacon for crispness. If golden and crisp, remove from the oven and transfer the bacon to a piece of paper towel to cool. Reserve the fat. If not, leave the bacon in the oven for a few more minutes, keeping an eye on it.
Meanwhile, thinly slice the potatoes into approximately ¼ cm thick slices. You can use a knife, mandoline (with the guard!), or your food processor with the slicing attachment. Add the sliced potatoes to a large pot and pour in the cream, milk, garlic, 3 thyme sprigs, and nutmeg and season with 1 teaspoon of salt and ¼ to ½ teaspoon of pepper. Place the pot over medium-high heat, cover with a lid, and bring to a boil. Boil for 2 minutes then remove the pot from the heat and set aside for 10 minutes to cool slightly. Remove the sprigs of thyme
Lightly grease a 9- by 13-inch casserole dish with non-stick cooking spray or the bacon fat. Chop the bacon, pick the thyme leaves from the remaining sprig of thyme, and toss with the grated cheese. Using a slotted spoon, scoop about a third of the potatoes from the cream and layer into the dish. Scatter with a third of the cheese mixture and repeat the layers until all the potatoes and cheese mixture are used up. Carefully pour the warm cream over the potatoes.
Lightly grease a piece of aluminum foil with non-stick cooking spray and tightly cover the dish. Bake the scalloped potatoes for 1 hour then remove the foil and continue to bake for 20 to 30 minutes or until the centre of the potatoes are tender and the top is golden.
Set aside for 20 minutes before serving or cool the potatoes to room temperature, cover, and refrigerate for up to 3 days. To reheat, set the potatoes at room temperature for 30 minutes. Cover and bake in the oven at any temperature between 325ºF and 400ºF for 30 minutes or until heated through.
