Sauce is often used in Western food, and you can also buy the finished product, so I will talk about the practices I have learned.
The first thing is to boil beef bone broth, that is, Brown stock, the way is to wash the beef bones, put them in the oven, between 180-230 degrees, so that it is colored, not burnt, otherwise the taste of the soup will be bitter. Move the roasted beef bones to a suitable vat, try not to bring oil, and then add the sautéed colored mirepoix, that is, onion, celery, carrot pieces, add spice packets, add water, usually boil for 6-8 hours, after boiling, filter, remove the oil, leaving the clear soup.
How to make a spice packet:
Spice packet is the Bouquet-garni in Western food, often used in boiling soup and stew, its method is to boil the green onion leaves in boiling water, over cold, wait for the green onion leaves to be soft, add thyme, rosemary, fragrant leaves, incense sticks, a little black pepper grains, wrapped into a bag, tied with cotton thread, can also be directly added to the bag, is often said in Western recipes "teabag"