Mashed potato au gratin

Peel and quarter russet potatoes; cover with cold water, salt generously, bring to a boil and cook on medium until very tender but not falling apart; drain well.

Meanwhile peel more potatoes for the top, halve them lengthwise and keep them covered in water.

Return the drained potatoes to the pot and mash fine; add butter, salt and a few shakes of cayenne and mash until smooth.

Stir in whole milk and a big handful of Comte; taste and adjust the salt.

Butter a casserole dish, press the mash into the corners and smooth the top; season the surface with black pepper and salt.

Slice the halved potatoes an eighth of an inch thick, guiding the knife with a finger and using a forward-then-back slicing motion; fan each sliced half and lay them in rows over the mash at a slight angle, covering the surface.

Salt the top generously, brush with plenty of melted butter, scatter grated Comte and grate Parmigiano Reggiano over.

Set on a sheet pan to catch dripping butter and bake in the center of a 450F oven for about an hour to an hour 15 minutes, until the potatoes on top are tender.