Set your oven to 200°C (400°F). A hot oven is the secret to crispy skin. Make sure the rack is in the center. Let it heat up fully before you start.

Wash your potatoes thoroughly under cold water. Use a brush to scrub off any dirt. Dry them completely with a clean towel. Wet skin will not get crispy in the oven.

Take a fork and poke holes all over each potato. This lets the steam escape while baking. It prevents the potatoes from bursting. Do about 8 to 10 pricks per potato.

Place potatoes on a tray. Drizzle them with olive oil. Rub the oil into the skin with your hands. Sprinkle plenty of sea salt and black pepper over them.

Place sprigs of rosemary or thyme on the tray. You can even rub the herbs against the oily skin. This adds a lovely woody aroma to the potatoes as they roast.

Put the tray in the oven. Bake for about 60 to 70 minutes. The time depends on the size of your potatoes. The skin should look dark and very golden.

Squeeze the potato gently with an oven mitt. It should feel soft inside. You can also use a skewer. It should slide in and out with no resistance at all.

Remove the potatoes from the oven. Use a knife to cut a deep cross in the top. Do not cut all the way through. This is the classic Gordon style.

Grip the base of the potato with a towel. Squeeze the sides toward the center. The white fluffy inside will pop up through the cross. It looks beautiful and rustic.

Drop a large knob of butter into the opening. Let it melt into the hot potato. Top with sour cream and fresh chives. Serve them immediately while they are piping hot.