Upside-down potato gratin with jus

Melt butter on low heat; when it begins to simmer, skim off the milk solids to make clarified butter.

Peel and chop the onion; smash and peel the garlic; chop fresh rosemary or thyme very fine.

In a sauté pan, sweat the onion with the bay leaf and olive oil about 15 minutes on low heat without browning.

Add the garlic, deglaze with the wine and reduce to dry.

Add the jus and cook down 10 minutes on low heat; discard the bay leaf and blend.

Fold a square of parchment into triangles, mark the pan's radius, cut and unfold to a circle that fits the cake pan.

Grease the pan and parchment generously with the clarified butter; peel the potatoes.

Slice the potatoes 2 mm on a mandolin, cut some into rounds with a cookie cutter, overlap them in circles on the bottom and sides of the pan and brush generously with butter.

Layer potatoes, jus mixture, pepper, herbs and parmigiano, repeating until done.

Cover with parchment and foil and bake at 350F / 180C for about 90 minutes; remove the parchment and foil and bake again.