Isn’t it forbidden from the Torah of Moshe to cook and eat the fat of kosher animals? If so is one obligated to remove all the fat from the meat before cooking it? פרשת ויקרא פרק ג
What you are referring to is the prohibition not to eat “helev”- which is a type of fat. There are two different types of fat in an animal, one type is called helev, and one type is called shuman, Helev is found around the kidneys, around the outside of the cows stomach, and in a few other places. Shuman is what is commonly found inside a piece of meat. Helev and shuman also have different textures to them, where helev is drier and flaky, but shuman isn’t. We only have to remove the helev but not the shuman. There is a special process and trade called “nikur”, which involves removing the forbidden fat and other parts of the animal that we don’t eat.