GET AHEAD

1. Peel the potatoes, keeping them whole, and ideally all about the same size (8cm). Parboil them in a pan of boiling salted water for 15 minutes – this will ensure that the insides become really fluffy.
2. Drain in a colander and leave to steam dry for 2 minutes – this will help the fat to stick to the potatoes. Give the colander a few light shakes to chuff up the edges of the potatoes, giving you maximum surface area for a crispy exterior as they roast.
3. Place the goose fat or butter and 1 tablespoon of oil in your largest roasting tray. Tip in the potatoes, add a good pinch of sea salt and black pepper, then toss to coat, and spread out in one fairly snug, even layer but with small gaps between them.
4. Cover and pop in the fridge overnight. Or, you can make these up to 1 month in advance – simply leave to cool, then cover and pop in the freezer.

ON THE DAY

1. Preheat the oven to 180°C/350°F/gas 4.
2. Squash the garlic bulbs, then lightly crush each unpeeled clove and add to the tray – this gives you sweet, caramelised garlic and adds a gentle perfume to the potatoes.
3. Roast for 1 hour, or until the potatoes are crisp and golden all over.
4. Remove the tray from the oven. We’re nearly there, but we’ve got one last application of love and care, which is the game-changer. Gently half-squash each potato with a fish slice or masher so they kind of push into each other and fill the tray.
5. Pick the sage leaves and – importantly – toss with a little oil (this will transmit the flavour and make them deliciously crisp). Sprinkle the sage over the potatoes and roast for a further 20 to 25 minutes, or until golden and amazing. Heaven – you could even serve these on their own in a restaurant, they’re so good.

For a tasty kitchen shortcut, check out Jamie's Garlic & Rosemary Potatoes from his new frozen range!