Boulangère potatoes

Method

1. Heat the oil in a wide pan over medium-low heat. Add the onions and 4 g salt. Cook for 30 to 40 minutes, stirring often, until deeply golden and jammy without black edges.
2. Heat the oven to 120°C. Line the base of the dish with baking paper and brush the paper and sides with melted butter.
3. Slice the potatoes 2 mm thick on a mandoline. Do not rinse them: their surface starch helps the layers bind.
4. Spread the onions over the base. Add overlapping potato layers, changing direction each time. Brush each layer lightly with butter, spoon over a little stock, and season sparingly with salt, pepper, and thyme. Finish with potatoes and reserve 20 g butter.
5. Press a baking-paper cartouche directly onto the surface. Top with a second dish or oven-safe plate that fits inside, then add a clean oven-safe weight.
6. Bake for 75 minutes. Remove the weight and cartouche, raise the oven to 130°C, and bake for 35 to 50 minutes more, until a knife passes through without resistance and most stock has reduced.
7. Brush with the reserved butter and a spoonful of reduced stock from the dish. Bake 5 minutes, then rest 10 minutes before cutting.

Notes

• Use a mandoline guard and stop before the potato becomes too small to hold safely.
• If the stock is salty, reduce the added salt. The finished dish should be savoury but not cured-tasting.
• Assemble up to six hours ahead and refrigerate; add 10 to 15 minutes to the covered bake.
• This recipe is reconstructed to a home-sized dish and remains needs-review until cooked in that vessel.

Sources used

• Fallow: Boulangère potatoes