1. Preheat the oven to 180°C/160°C fan/gas 4. Put the stock and butter into a saucepan and heat to gently simmering.
2. Meanwhile, use the mandoline on its thinnest setting to slice all the potatoes thinly, then stack them up in a small baking dish so they fit snugly – don’t worry about being too neat, you need to work quite quickly so the potatoes don’t brown.
3. Once you’ve stacked all the potatoes into the dish, pour over the stock mixture and season well. Tuck the rosemary sprigs in and transfer to the oven to bake for 45 minutes-1 hour, until the potatoes are cooked through and crisp on top, and the stock is bubbling around the sides. Leave to stand for 5 minutes, then serve.
See more Potato recipes
Cook’s tip: If you don’t have a mandoline, then slice the potatoes as thinly as possible, and boil them for 2 minutes then drain and allow to steam dry before layering them up to bake.