The Demi-Glace Base

The Demi-Glace (half-glaze) is a rich brown sauce base prepared by combining a reduced brown stock and the ‘mother’ sauce Espagnole. This Espagnole is one of the five mother sauces of Escoffier. The sauce is boiled down to about one-third to a half of the original volume.

The demi-glace forms the basis for other sauces such as Sauce Robert. 

The phrase demi-glace or half-glaze comes from the rich glossy coating that forms when such a sauce is poured over meat. The french for glace is ‘icing’ or ‘glaze’ which describes the appearance of the sauce.

The original sauce and probably one that still needs to be prepared requires plenty of veal bones. A vegetable selection is added to create another flavour layer often known as the mirepoix. A typical recipe for this type of brown meat stock is simple but easy to mess up.

It is not the same as a glace de viande which is a brown stock that is reduced to a glaze although they can often be substituted for each other in certain applications. The level of reduction is about 6 to 8 times smaller than the original volume.  The demi-glace is often diluted to prepare a stock but it makes an effective base for a wide range of brown sauces.

The process of manufacture is lengthy but worth the effort. Julia Childs developed a recipe which deviates from the original but remains a viable alternative because of the effort needed to produce the original demi-glace.

Ingredients:

• 2 – 3 kg/4 – 6 lbs of veal bones
• 1 kg mirepoix (500g of chopped yellow onions, 250g of diced carrot and 250g of celery).
• 2-3 bay leaves
• 8-10 black peppercorns

Preparation:

1. Put the veal bones in a large stock pot and add between6 and 7 litres of water. Enough to cover the bones plus enough to cover them.
2. Bring to the boil and skim off the foam and scum that forms. A couple of times will be enough.
3. Add the vegetables, bay leaves and peppercorns.
4. Reduce the heat to a simmer and cook for up to 14 hours. The demi-glace is best started in the morning. Keep adding water above the bones level as its simmers.
5. Drain off the stock through a medium-mesh sieve or strainer. Most chefs would press on the bones and vegetable mash to extract as much protein as gelatin as feasible.
6. Put all the bones and cooked mirepoix back in the stockpot and add a further 3-4 litres of water. This is called the remoulage. Resume the boiling and simmering process for another 4 hours.
7. Strain this stock through a finer sieve if available.
8. Discard the contents.
9. Rapidly cool the stock if possible or just refrigerate.
10. When the stocks are cool enough, skim off any solidified fat. the stock at this point may also be a lightly structured gel.
11. Combining both stocks, reboil rapidly until it is reduced by a half. 
12. Store in resealable freezer bags or large containers. A volume of 2 litres should be possible.