Each potato is sliced very thinly almost all the way through, then the potatoes are set snugly in a row and brushed deep between the slices with melted butter, garlic, thyme, salt and pepper.
The gratin comes from cheese, not cream. After a covered bake, the slices are fanned, Gruyère is tucked between and over them, and Parmesan goes on top for a final browning in the oven.
Why This Recipe Works
- Leaving the base intact holds each potato together while the slices fan open.
- Baking under foil first steams the centres tender before the cheese goes on.
- Tucking Gruyère between the slices melts it into the potato, while Parmesan on top browns into a crust.
- Brushing the butter deep into the cuts seasons the whole potato, not just the outside.
Slice, Steam, Brown
Stage 1 of 3
Slice and butter
Steps 1–2 of 5
Potatoes cut thinly almost to the base, set in a row and brushed deeply with garlic-thyme butter.
- Potatoes sliced hasselback-style and lined upHeat the oven to 400°F and butter a narrow baking dish. Slice each potato very thinly almost all the way through, keeping the base intact, then arrange them snugly in a row.
- Garlic-thyme butter brushed between the slicesMix the melted butter, garlic, thyme leaves, salt and pepper and brush it deep between the potato slices.
Stage 2 of 3
Covered bake
Steps 3–3 of 5
Thirty minutes under loose foil so the centres soften.
- Baked covered for 30 minutesCover loosely with foil and bake 30 minutes.
Stage 3 of 3
Cheese and browning
Steps 4–5 of 5
Slices fanned, Gruyère tucked in, Parmesan on top, and baked uncovered until the cheese is deeply browned.
- Slices fanned, Gruyère and Parmesan addedRemove the foil, gently fan the slices, tuck the Gruyère between and over the potatoes and sprinkle with Parmesan.
- Baked until browned, moved to a platterBake another 20 to 25 minutes, until the potatoes are tender and the cheese is deeply browned. Move carefully to a platter with the buttery pan juices and garnish with thyme sprigs.
How to Make It
Potatoes sliced hasselback-style and lined up
Heat the oven to 400°F and butter a narrow baking dish. Slice each potato very thinly almost all the way through, keeping the base intact, then arrange them snugly in a row.
Garlic-thyme butter brushed between the slices
Mix the melted butter, garlic, thyme leaves, salt and pepper and brush it deep between the potato slices.
Baked covered for 30 minutes
Cover loosely with foil and bake 30 minutes.
Slices fanned, Gruyère and Parmesan added
Remove the foil, gently fan the slices, tuck the Gruyère between and over the potatoes and sprinkle with Parmesan.
Baked until browned, moved to a platter
Bake another 20 to 25 minutes, until the potatoes are tender and the cheese is deeply browned. Move carefully to a platter with the buttery pan juices and garnish with thyme sprigs.
Ingredient Notes
- Yukon Gold potatoes
- Two and a half pounds, peeled and sliced very thinly almost to the base.
- Gruyère and Parmesan
- A cup and a half of Gruyère tucked between the slices and a third of a cup of Parmesan over the top.
- Garlic-thyme butter
- Four tablespoons of melted butter with two grated garlic cloves and a teaspoon of thyme leaves.
Success Tips
- Lay a chopstick on each side of the potato while slicing to stop the knife before the base.
- Brush the butter mixture right down into every cut.
- Use a wide spatula to move the row to the platter in one piece.
Frequently Asked Questions
Is there a cream sauce?
No. The gratin crust comes from browned Gruyère and Parmesan, with butter.
How do I know the potatoes are done?
A knife slides easily into the centre of each potato and the cheese is deeply browned.
Serving Ideas
Carry the whole row to the table on a long platter, spoon the golden butter from the dish around it and add thyme sprigs.
