Layered sweet potato casserole with leeks, walnut meal and parmigiano

Mince the leek, soak in lukewarm water and drain.

Sweat the leeks in butter with salt and pepper, covered, 5 minutes on medium heat.

Grind walnuts (or other nuts) to a meal.

Uncover the leeks, add the stock or chardonnay and cook until reduced by half; add heavy cream and reduce by half again.

Scrub the yams under running water, trim the tips, peel and cut into 4 mm slices with a mandolin or chef's knife.

Line a terrine mold with parchment paper; layer overlapping sweet potato slices, season lightly with salt and pepper, then add some leek mixture, walnut meal and parmigiano reggiano. Repeat until full.

Cover with the lid or aluminum foil and bake at 350F / 180C for an hour.

Press with a weight on top, leave at room temperature at least 3 hours, then refrigerate overnight.

Run a spatula around the edges, flip, warm the bottom of the mold with a kitchen blowtorch to unmould, remove the parchment and cut into 8 portions.

Serve hot with fried sweet potato skins.