For example, most margarines are dairy for kosher purposes, because they contain a small quantity of whey or other dairy products to give it a dairy-like taste. Therefore, a kosher kitchen must have two separate sets of pots, pans, plates and silverware – one for meat/poultry and the other for dairy foods. All kosher milk products must come from kosher animals, and dairy products can't contain animal-based ingredients. The rules of keeping a kosher kitchen would include keeping dairy plates, pots and utensils separate from those used for eating or cooking meat. With its roots in the Hebrew Bible, the system of defining which foods are kosher was developed by the rabbis of late antiquity. One of the important aspects of observing kosher is keeping milk and meat properly separated.
↑ Shach 95:20 isn't certain whether we assume that an iruy cooks so much to infuse the taste of the meat into the dairy dish and then extract the non-kosher taste from the dairy dish and infuse it back into the meat dish. Summary Kosher guidelines strictly prohibit the pairing of any meat and dairy product. In this particular case, the Torah forbade meat (of kosher mammals) and milk (of kosher mammals). Keeping a kosher home, means the same thing. He concludes that we should be strict unless there's a large loss. Kosher meat is always cooked well done so that no pink is left. Animal fat is considered meat for purposes of kashrut. Animal fat is considered meat for purposes of kashrut. Note that even the smallest quantity of dairy (or meat) in something renders it entirely dairy (or meat) for purposes of kashrut. As long as a pot is clean, and no longer has pieces of meat in it, there’s no problem with cooking a piece of fish in a pot previously used to for a roast. The Torah states that "You may not cook a young animal in the milk of its mother," and therefore Jews do not consume milk and meat together in the same meal, and use different plates, utensils, and cooking tools for milk and meat. This also means that all utensils and equipment used to prepare meat and dairy …

Kosher kitchens generally have separate sets of dishes and utensils for dairy and meat, but fish does not require these same extreme measures.

Ask an average person to describe kosher food and they might say it is food “blessed by a rabbi.” The word “kosher,” however, is Hebrew for “fit” or “appropriate” and describes the food that is suitable for a Jew to eat. The rabbis added a fence to the basic halacha by including (kosher) birds because people treat birds as meat in the ame way as animals (unlike fish). As a safeguard, the Sages disallow the eating of meat and dairy products at the same meal, or preparing them with the same utensils. Published Spring 2008 One of the best known halachos of kashrus is that one may not eat meat and milk together.

The practice of not eating dairy products with meat comes from the Torah prohibition again cooking a kid (baby goat) in its mother's milk. The blood of any animal is trayf, so kosher meat (except for fish) has to be kashered (made kosher) by draining the blood and washing and salting the meat. For example, most margarines are dairy for kosher purposes, because they contain a small quantity of whey or other dairy products to give it a dairy-like taste. This prohibition is derived from the verse, "Do not cook a kid in its mother's milk." One of the reasons that kosher symbols incorporate a ‘D’ onto the kosher certification is to notify the consumer that the product may not be eaten together with meat, or within six hours after eating meat. – sabbahillel Jun 23 '17 at 22:19
Note that even the smallest quantity of dairy (or meat) in something renders it entirely dairy (or meat) for purposes of kashrut.