This particular sauce is prepared in two steps. An organized mise en place and proper timing is essential, not only to execute the sauce perfectly but also to achieve the desired consistency.
Quarter onion
2 Garlic Cloves
Half a Carrot
Half a Celery Stick
2 Tablespoons Tomato Puree
1 Cup Chicken/Beef Stock
A Pinch of Nutmeg Powder
Half Teaspoon Flour
Butter
Olive Oil
Salt for Seasoning
Start with the foundation of the sauce. In a deep pan melt a heaping teaspoon of butter. To it add half a teaspoon of flour and mix well. Be careful not to burn the butter so do not leave unattended. Butter does burn very quickly so control the heat at all times. If need be, take the pan off the heat occasionally while continuously stirring. Since this is a brown sauce, ideally a deep brown beef stock should be used, but a simple chicken stock will also do. Once the flour and the butter have mixed well and the butter starts to brown ever so lightly, add about one third of a cup of stock and whisk. Let the liquid reduce a bit and then add another third of a cup of stock, and continue whisking making sure all lumps are gotten rid of. Again pay close attention to the heat and keep it controlled. Now the sauce begins to take shape. Add in a decent pinch of nutmeg for flavor, but do not go overboard as a little pinch goes a long way. Finally add in the last third of the stock and whisk it well to ensure a smooth sauce with no lumps. Set the sauce aside and move on to the next step.
Finely chop a quarter of an onion, a couple of cloves of garlic, half a carrot and half a celery stick, and set aside. In a pan melt a small knob of butter with a little bit of olive oil and sauté the chopped garlic on a medium low heat. When the aroma of the garlic comes through, add in the onions and continue sautéing till the onions become translucent. After a couple of minutes of sautéing, add in the chopped carrots and celery. Toss around till the vegetables soften a bit. At this point add a couple of tablespoons of tomato puree, and season with a pinch of salt. Once all the ingredients in the pan have amalgamated, add in the brown sauce, a tablespoon at a time and mix well. Another tablespoon of tomato puree can also be added should the need arise. Once all the sauce is added to the vegetables, mix well and continue cooking for a minute or so. Turn off the heat and then transfer all the ingredients in the pan to a sieve. Sieve well making sure all the sauce passes through, and then stir the sauce around to combine all the flavours together.
The same sauce can also have mushrooms incorporated into it, in addition to a few tweaks. The first part of the sauce i.e. the foundation remains the same. The entire second part of the recipe changes. Finely chop a couple of button mushrooms, a couple of cloves of garlic and quarter of an onion and leave aside. In a pan heat a tablespoon of olive oil and a knob of butter. The olive oil stops the butter from burning too quickly. When the butter has melted add in the chopped garlic and sauté for a couple of minutes. Then add in the onions and continue sautéing till the onions become translucent. Once that happens add in the mushrooms and season with a pinch of salt and pepper. Mix all the ingredients well and finally add a tablespoon of cream. Once all this is done, add in, a tablespoon at a time, the brown sauce. When everything is mixed together well pass through a sieve making sure all the sauce passes through.