Slice the peeled potatoes into thin slices, about 3mm/⅛in thick. Place the slices into a bowl as you cut them.
Trim the ends off the garlic cloves but don't peel. Grate the cloves on a grater. The flesh will go through the fine holes and the skins will be left behind. Scrape the grated garlic flesh into the bowl with the potatoes.
Season the potatoes, to taste, with salt and freshly ground black pepper. Pour the cream over the potatoes and mix well again.
Place the potato slices into the GN container. They should come to just below the top of the dish. Press the potato down with the back of another GN container. The cream should come to just below the top layer of potato (top up with more double cream if necessary).
Place the potatoes in the oven and bake for 1hour and 15 minutes hours at 140°C, or until the potatoes are completely tender.