A simple stock reduction refers to glace de viande (pronounced glahs duh vee-AHND). Traditional demi-glace is much more involved, literally means half glaze, and requires even more hours in the kitchen babysitting stock. It is half stock and half Espagnole (pronounced ehs-pah-NYOHL) sauce that are then reduced by half. This traditional method is a little passé according to an article on StyleForum, which suggests that reductions are hot and roux is not. But some believe that the time spent on making demi-glace the traditional way using both brown stock and Espagnole sauce is well worth it.
So, what is Espagnole sauce? Espagnole sauce is the most basic brown stock in French cuisine, has the distinction of being one of the five mother sauces, and has a Spanish name. You can credit the Spanish cooks at Louis XIII’s wedding who added Spanish tomatoes to the brown sauce and everyone loved it. I'm sure these cooks would have given the Iron Chefs a run for their money with their Spanish tomatoes!
Espagnole sauce is made with brown roux and brown stock. Bacon, the usual aromatics (onions, celery, carrots, a Bouquet garni), and tomatoes are added. Also, Madeira or sherry is sometimes added, although the recipe I used didn’t call for it.
Process for Demi-glace
So, here’s the process to make classical demi-glace:
1. Make brown stock.
2. Make Espagnole sauce.
3. Make demi-glace.
Since I have a freezer full of stock, I just had to prepare the Espagnole sauce to get to step 3.
Thomas Keller’s Veal Stock and Demi-glace
When I made veal stock, I made several versions. To make the demi-glace, I used one of the veal stocks that I roasted with tomato sauce. As I was working through this recipe, it occurred to me that Thomas Keller’s veal stock involved a similar 2-step plus reduction process. His doesn't have a whiff of flour in it nor does it have bacon, but other than that I wonder if you might be able to classify it as demi-glace.
So, you can try the following three ways to get yourself to demi-glace status:
• You can reduce veal stock. This is more common these days since roux is passé and reductions save time in the kitchen. But, for the purist this is not the path to flavor nirvana.
• You can follow the Keller way, which is to make a "veal stock #1", and then make a "veal stock #2". Then you can reduce that down to make a demi. (Keller’s stock has a more tomato-y flavor, and if you want the smoky flavor that an Espagnole sauce has, you could add the bacon in the last step.)
• You can follow the traditional method and make a stock, make an Espagnole sauce, and then make a demi.
Recipe for Espagnole Sauce
Adapted from La Varenne Pratique and here
Makes 1½ cups
3 tablespoons butter
¼ cup flour
4 cups brown stock
2 ounces bacon, diced
½ onion, diced
½ carrot, diced
1/8 cup tomato purée
1 Bouquet Garni
Salt and pepper
Heat the butter in a heavy saucepan. Add the bacon and sauté for 2-4 minutes. Add the onion and carrot and sauté until soft. Add the flour and cook gently until the mixture is a dark brown, about 5 minutes.
Meanwhile, bring the brown stock to a boil. Cool the vegetable mixture slightly and then whisk in ¾ of the stock. Bring to a boil, whisking until the mixture thickens.
Add the Bouquet Garni and tomato purée. Simmer gently uncovered for 3-4 hours. Skim and stir occasionally. Add the remaining stock gradually during cooking, skimming as you do.
When the sauce has reduced by half, strain. Season to taste.
Tip for checking if your mixture is reduced by half:
Use a ruler.
Stick it in the pot when all the liquid is in and note where the liquid comes to on the ruler. Then, mark on the ruler with a pen the halfway point. While it reduces, stick the ruler in to check to see if it's reached the half-way mark.
Recipe for Demi-Glace
1 cup brown stock
1 cup Espagnole sauce
1 Bouquet Garni
salt and pepper
In a heavy stock pot, combine the Espagnole sauce, brown stock, and Bouquet Garni over medium-high heat until the mixture is reduced by half, about 1½ hours. Skim occasionally. Season with salt and pepper. Strain.
This is an involved process, but definitely worth it. It takes a day to make the stock, another half day to make the Espagnole sauce and the demi-glace. The sauce I made with this demi-glace was amazing. I sautéed some mushrooms, poured in a ladle-full of demi-glace and “easy” as that, I had a rich, velvety, delicious sauce that was out of this world.
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Running total: $434.84 + $2.07= $436.91
Butter used so far: 5 pounds, 5 tablespoons