Demi-Glace
A 48–72 hour reduction, done properly
The sauce base. Use about 4 frozen cubes.
A demi-glace truffle sauce on spaghettini, with cold-pan duck breast and a bitter leaf salad
Sauce Périgueux is the classical French truffle sauce. It is built on demi-glace, not on butter. Here it dresses spaghettini, and a seared duck breast goes beside it. The truffles are jarred pieces in oil. They go into the sauce off the heat, because their aroma compounds are volatile. Pecorino goes on top for acidity. A rocket salad with lemon cuts the richness.
First version. Written from a planning session. It was not cooked before it was stored.
Take the duck breasts out of the refrigerator 30 min before you cook them.
Cut the skin in a crosshatch, with cuts 5 mm apart. Cut through the fat, but not into the meat.
Dry the skin fully with kitchen paper.
Put 2 g of salt on the meat side only. Do not salt the skin.
Set the heat to medium-low. Cook for 12 to 15 min to render the fat.
Pour the fat into a bowl two or three times during this step. Keep it for roast potatoes.
Bring 3 L of water to a full boil in a large pot. Add 30 g of salt.
Do this while the duck renders.
When the skin is deep gold and crisp, turn the duck. Cook the meat side for 3 to 4 min.
Remove the duck when the centre reads 54 °C.
Rest the duck skin side up and uncovered for 8 min or longer. Make the sauce and pasta now.
The centre rises to about 57 °C during the rest. A cover traps steam and softens the skin.
Pour the fat out of the duck pan. Keep the brown residue in the pan.
Melt the demi-glace in the duck pan over medium-low heat. Do not reduce it.
Put the spaghettini in the boiling water. Cook it 1 min less than the time on the packet.
Add the Madeira to the melted demi-glace. Simmer for 2 to 3 min.
Pour the juices from the resting duck into the pan.
Remove the pan from the heat.
Add 25 g of truffle pieces and 15 ml of the jar oil. Stir gently. Keep 5 g of pieces back.
Do not put the pan back on high heat after this step. Heat drives off the truffle aroma.
Toss over the lowest heat for 60 to 90 s, until the sauce is glossy and holds to the pasta.
If the sauce is too thick, add pasta water 15 ml at a time.
Add the black pepper.
Toss the rocket with 15 ml of lemon juice and the olive oil. Coat the leaves lightly.
Cut the duck across the grain at a steep angle, into slices 5 mm thick.
Put the spaghettini in the centre of warm bowls. Put the duck slices beside it.
Put the 5 g of kept truffle pieces on the pasta.
Grate the pecorino over the pasta.
Serve the salad on a side plate. Serve at once.
The truffle aroma drops quickly after plating.
If you cannot get duck breast, use a skin-on chicken thigh with the bone removed. Use the same cold-pan method. The dish loses the iron and mineral taste of duck, which pairs well with truffle.
Madeira is the classical wine for Périgueux. Dry sherry (fino or amontillado) is the next best. Dry red wine also works: simmer it 1 min longer so the tannin softens.
Made to replace a Gordon Ramsay truffle butter sauce. That sauce showed the truffle, but the taste was flat. The brief was to showcase jarred truffles, and not to make a dish that is fully Italian.
A 48–72 hour reduction, done properly
The sauce base. Use about 4 frozen cubes.
What is actually happening in the dish, and why the techniques work.
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:
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.