Remove a straight slice from each edge of the potato in order to make sure we have a straight base.
With a good chef’s knife, slice the potato into slices but not all the way. In other words - cut nearly to the base – but stop, so the potato is sliced but attached at the end (take a look at the picture). The thickness of each slice should be slightly less than half an inch.
Place the potatoes in a small dish with high sides.
By hand - give each potato a squeeze gently so that it forms a light shape of a "Fan"
Pepper gently but sparingly on potato and sprinkle on a little thyme.
Cut the butter into small “blocks” - and place two small “blocks” on each potato.
Fill the pan with the beef stock to cover the potatoes.
Cover the dish with aluminum foil and make a few ventilation holes with a toothpick.
Heat oven to 180 degrees.
Cooking time is up to you - in fact after an hour - the potatoes will be ready. But you can leave them in the oven as long as there is liquids - and the more you leave them aligned evaporating - they will be crispier. So prepare yourself a cup of tea and let’s move on to take care of the main course. Whoever loves their potatoes crispy and has no patience – they can start baking without covering for about half an hour - and then continue cooking covered.
When it is ready, strain the liquids and serve alongside a main dish.