In 1926 a biologist named Haldane wrote an essay on “being the right size”, this essay surface, volume and the interaction with heat and pressure and other natural forces. His basis is; air is resistance to movement is proportional to an object’s size. Believe it or not this has implications on making of a stock, it impacts time and flavor.
So why is mirepoix important. The answer is; when you dice a vegetable, you get smaller particles, the greater the number of smaller particles, the greater the expansion of flavor based on diffusivity. Flavor molecules diffuse and flavors get extracted by the square of the smallest dimension.
Making the modern stock is simple; instead of getting large bones, get meat ground up, get bones that are cut into the small sizes. The smaller the ingredients, the less time required to make the stock. Put it this way, most of the flavor is extracted from bone or vegetable within the first hours. The rest of the time you are evaporating water, retaining the flavors and concentrating.
When you use a pressure cooker, you raise the temperature of boiling by as much as 20% or more, hence the higher temperatures. The liquid inside will not boil, a liquid boils when vapor pressure exceeds the ambient temperature around it. A stock that does not boil will be more clear, and clear is key, the boiling emulsifies and makes the end result poor. When you use a pressure cooker, you want to avoid steam from streaming from the value, as this means you are boiling and the pressure needs to escape or blow up, so the valve lets it evacuate.
Making a stock is all about extracting flavor. In French cuisine the saucier is one of the most important people in a French kitchen, and their secrets are well guarded.
Each time a stock is made a mirepoix is used according to the following ratio of 2:1:1, onions, carrots and celery. The next step is the meat and bones, five to seven times the volume of the mirepoix. The bones are browned often with some tomato paste, later place it all together into a large pot and cover with water, simmer slowly for hours and hours. The last step involves straining the stock.
So let’s go:
Step 1: Prepare materials by dicing them into a mirepoix.
Materials: Water 1000g, Sweet Onions or leeks 100g, 50g Carrots and 50g celery, Italian Parsley 3g, Black Peppercorns 1g – Chicken bones/wings 700g and ground chicken meat thigh 700g.
Step 2: Blanch the chicken bones starting in cold water and bringing to a boil, then discard the water. Alternatively you can brown the bones which is the classical way. It is believed that blanching gives a more pure and clearer taste.
Step 3: Combine the water, mirepoix and other materials.
Step 4: Pressure cook at 1 bar/15psi for one hour and a half. The starting time is when you have the pressure inside the cooker at 1 bar – a pressure bar is needed for the pressure cooker.
Step 5: cool off pressure cooker and strain through a very fine sieve.
Variation of Brown Stock is just as simple: at step 2, take 75g of neutral frying oil and roast the chicken bones in at 190°C until they turn brown, and take the ground chicken meat and pan fry it golden brown. Then add the materials all together into the stock. If you have the carcass of the chicken you can use it as well but blanch it or brown it, and remember the cleaner the meat the cleaner the flavor.