Sauce Périgueux Spaghettini with Seared Duck Breast

Most truffle aroma is volatile sulphur compounds, such as dimethyl sulphide and bis(methylthio)methane. These dissolve in fat.

Butter dissolves them, but it gives them no background. The sauce tastes rich but empty.

Demi-glace does three things that butter cannot:

• Gelatin. It makes the sauce thick. The sauce stays on the tongue longer, so the aroma stays longer.
• Glutamate. The reduced stock is high in free glutamate. The truffle then reads as deep, not only as a smell.
• Maillard compounds. The roasted bones and the long reduction give a complex brown background. The truffle sits on top of it and does not disappear into fat.

Truffle aroma compounds are small and volatile. On a hot pan they leave the sauce as vapour before the dish reaches the table.

The warm demi-glace has enough heat to release the aroma into the fat of the sauce. It does not have enough heat to drive the aroma off. The kept pieces on top of the plate release their aroma from the heat of the pasta, at the moment the dish is served.

Duck breast has a thick layer of fat under the skin. In a hot pan the skin browns before this fat melts. The result is burnt skin over a layer of soft fat.

A cold pan heats the skin slowly. The fat melts and runs out before the surface reaches browning temperature. The crosshatch cuts give the fat a path out and add surface.

Salt on the skin pulls water to the surface, and water slows crisping. Salt the meat side only.

Parmesan adds more glutamate. The sauce already holds a lot of glutamate from the demi-glace, so parmesan makes the dish heavier and less clear.

Pecorino is sheep milk cheese. It is sharper and more acidic. The acidity gives a bright edge next to the truffle.