Hasselback Potatoes

Doneness

Done when a knife or fork slides into the centre with no resistance, the fanned slices have splayed open, and the edges are deep golden and crisp. The inside should be soft and fluffy while the tops of the slices crackle. Thick potatoes that still feel firm in the middle need another 5–8 minutes — keep cooking rather than raising the heat, which only burns the fanned tops.

Oil & seasoning

Yes — brush or spray oil or melted butter generously into the cuts and over the top, then again partway through. The slits dry out and the fans won't crisp without it. Getting oil down between the slices is what makes the edges shatter-crisp.

Season with: Garlic-herb butter (the benchmark): melted butter with minced garlic, rosemary or thyme, salt and pepper, brushed into the slits before and after cooking., Parmesan: tuck thin shavings or sprinkle grated parmesan between the slices for the last 8 minutes so it melts into the fans., Loaded: top the finished potatoes with crumbled bacon, shredded cheddar and chopped chives, like a fanned twice-baked., Ranch: toss with ranch seasoning before cooking and finish with a drizzle of ranch dressing..

Watch out for

• !Don't slice all the way through — rest the potato between two chopsticks or wooden spoon handles so the knife stops about ¼ inch from the bottom and the slices stay attached.
• !Brush oil or butter down into the cuts, not just on top, or the slices dry out and never fan open or crisp.
• !Use medium, uniformly sized potatoes (Yukon Gold or russet) so they cook through evenly; very large ones need extra time and may burn on top before the centre softens.
• !Gently fan the slices apart with a fork partway through so the heat reaches the inner edges and they crisp instead of steaming shut.
• !Check the centre with a knife before serving — the fanned tops brown fast and can look done while the middle is still firm.