Pommes Anna

Method

1. 1Clarify the butter: melt 100 g unsalted butter over low heat, skim the foam, and spoon off the clear golden fat, leaving the milky residue behind. You need about 80 g.
2. 2Peel the potatoes and slice them 2 mm thick on a mandoline. Do not rinse them; the surface starch is what binds the layers. Pat dry only if visibly wet.
3. 3Brush a 24 cm oven-safe nonstick or well-buttered cast-iron skillet with clarified butter and heat the oven to 220°C.
4. 4Place one slice in the centre, then lay overlapping slices in concentric circles, each covering the previous by about half. Brush with clarified butter and season lightly with salt, pepper and, if you like, thyme.
5. 5Repeat for 3 to 4 layers, brushing butter and seasoning between each. Press firmly with the base of a second pan to compact the cake.
6. 6Set the skillet over medium heat for 3 to 4 minutes to set and brown the bottom layer.
7. 7Move to the oven and bake about 45 to 50 minutes, pressing once more halfway through, until the edges are golden and a knife slips through easily.
8. 8Pour off the excess butter, run a knife around the edge, invert onto a plate, and cut into wedges. Serve hot.