Pre-heat the oven to 200.c /180.c Fan
Peel the potatoes then cut them up into largish pieces, roughly egg size is good. Rinse the prepared potatoes in several changes of fresh cold water, which helps to remove excess starch. Place the spuds in a large saucepan, cover with plenty of salted water and set them over the heat. Bring the potatoes up to the boil, turn down the heat and simmer for 8 to 10 minutes or until they are just tender.
Don’t let them start to break up though. Drain them into a colander then allow them to steam off, for at least 5 or 10 minutes. It’s well worth tumbling the potatoes around in the colander, once or twice, to rough up their edges, it makes them even crispier. Meanwhile spoon the dripping into a large heavy based baking dish and place it in the oven to heat up. When it’s lovely and hot, carefully turn the potatoes out into the tray. Use a spatula to turn them through the beef fat then make sure they’ve all got a little space.
Sprinkle them all over with sea salt and season them with freshly ground black pepper. Place them in the middle of the hot oven and roast for 25 – 30 minutes turning once. At this point lift tray out of the oven and carefully press the potatoes to squish them lightly. A potato masher or back of a serving spoon will work well for this task. add the garlic, rosemary and thyme and turn together. Cook for a further 25 – 30 minutes or until the potatoes are lovely and crisp and golden. Use a slotted spatula to lift the potatoes out of the tray onto a large warm plate and bring to the table.