Photograph: Jonathan Gregson
Preheat the oven to 200°C, fan 180°C, gas 6. Gently heat the dripping and herbs in a pan so the dripping melts and the herbs infuse.
Put the potatoes in another pan, cover with cold water. Cover, bring to the boil and simmer gently for 15 minutes until the potatoes are almost cooked. Drain in a colander and shake well, then leave to dry. Scratch all over with a fork to roughen them.
Put 1 or 2 large shallow roasting tins in the oven for 10 minutes. Carefully remove them from the oven and pass the herb-infused dripping through a sieve into them. Discard the herbs. Return the tin/s to the oven for 5 minutes, then remove and carefully add the potatoes, one by one. Season with salt, then roast for 35-40 minutes until crisp and golden, turning every 10 minutes. Sprinkle with sea salt halfway through cooking.
With a slotted spoon, transfer the potatoes to paper towels to soak up the excess oil. Serve immediately.
Get ahead: infuse the dripping a day before. Parboil the potatoes a few hours ahead.
Kitchen secret: roughing up the edges of the potatoes ensures you have the maximum surface area hitting the hot fat, making the crunchiest possible potatoes.