Ten ingredients and an hour and forty minutes, and the first forty of those are one pan of onions on medium-low.
The cheese is inside rather than on top. Small amounts of Gruyère go between the potato layers, which is why the finished surface shows onions rather than a melted crust.
Why This Recipe Works
- Thirty-five to forty minutes on medium-low is what takes onions to deep brown rather than soft.
- Slicing the potatoes thinly means they cook through in the covered stage.
- Cheese between the layers seasons the whole dish without forming a lid.
- Pouring the liquid around the edges lets it absorb rather than pool on top.
- Uncovering for the last twenty-odd minutes is what browns the potato edges.
Ingredient Notes
- Three large yellow onions
- Thinly sliced and cooked down for the best part of forty minutes. They are the dominant thing on the finished surface.
- Gruyère
- A cup shredded, in small amounts BETWEEN the layers rather than over the top. That is what keeps the surface onion-dark.
- Yukon Gold potatoes
- Two pounds, sliced thinly into rounds. Rounds rather than cubes or mash, and thin enough to cook through under a lid.
- Stock and cream
- Half a cup of each, poured around the edges. Enough to be absorbed rather than to leave a pool.
How to Make It
Onions, thirty-five to forty minutes
Cook onions slowly in butter and olive oil with half the salt over medium-low heat for 35 to 40 minutes until deeply caramelised dark brown.
Layer rounds, thyme, Gruyère, onions
Heat oven to 375 degrees Fahrenheit. Layer potato rounds in a buttered baking dish with black pepper, thyme, small amounts of Gruyère between layers, and the caramelised onions.
Liquid around the edges, not over the top
Pour stock and cream around the edges; the liquid should absorb during baking rather than pool on top.
Covered thirty-five, then uncovered twenty to twenty-five
Cover and bake 35 minutes, then uncover and bake 20 to 25 minutes more until potato edges brown and the onions remain dominant on the surface.
Rest ten minutes, no meat and no crumb
Rest 10 minutes before serving. Do not add meat or breadcrumb topping.
Forty Minutes Before the Oven, and Cheese You Cannot See
The title says cheesy and the photograph shows no cheese at all. The answer is the third rung below - and the first is where most of the recipe's actual time goes.
Caramelise, slowly - this is the recipe35 to 40 minutes, medium-low, dark brown
3 large yellow onions, thinly sliced, in 3 tbsp butter and 1 tbsp olive oil with HALF of 1 tsp salt, over MEDIUM-LOW heat for 35 TO 40 MINUTES until DEEPLY CARAMELISED DARK BROWN. This is nearly half the total time and it happens before the oven is switched on. There is no shortcut: high heat browns the edges and leaves the rest raw-tasting, and merely softened onions would give a pale dish.
Slice thin, and keep them rounds
2 lb of Yukon Golds sliced THINLY INTO ROUNDS. Thin because the covered stage has to cook them through; rounds because that is the shape of this bake - not mashed, and not cubed.
The cheese goes INSIDE
1 cup of Gruyere in SMALL AMOUNTS BETWEEN THE LAYERS, with 1/2 tsp black pepper and 1 tsp thyme, and the caramelised onions layered through. This is where the cheesy of the title lives - but it sits between the potato rounds rather than forming a browned lid, which is why the top shows onions and no melted crust. Scattered over the surface instead, it would give a different dish.
Liquid at the EDGES
1/2 cup of stock and 1/2 cup of cream poured AROUND THE EDGES rather than over the top. The liquid is meant to be ABSORBED during the bake; poured over the surface it sits there, and there should be no pooled cream visible.
Covered, then uncovered - two different jobs35 covered, then 20 to 25 uncovered
35 minutes COVERED at 375F to steam the potato through, then 20 to 25 minutes UNCOVERED until the POTATO EDGES BROWN and the onions REMAIN DOMINANT on the surface. The lid cooks; the open oven colours. Then 10 minutes of rest, and step 5 adds nothing: no meat, no breadcrumb topping.
Success Tips
- Do not rush the onions; medium-low for the full forty minutes is the recipe.
- Slice the potatoes thinly and evenly so they finish together.
- Pour the liquid at the edges rather than over the top layer.
Serving Ideas
Six servings from the dish, the sliced potato rounds under their heavy layer of deeply caramelised dark-brown onions with thyme sprigs, browned and crisp at the edges.
Frequently Asked Questions
Where is the cheese?
Between the layers. Gruyère goes in small amounts between the potato rounds rather than as a browned top, which is why the surface shows onions instead.
Can I shorten the onion step?
Not really. Thirty-five to forty minutes on medium-low is what makes them deeply caramelised and dark brown, and that colour is the dish.
Can I add bacon or a crumb topping?
No — step 5 rules out both meat and a breadcrumb topping.
