I have taken beef fat and rendered it down on lower / medium heat. usually I cut thin strips and add them as the rendering process occurs, and remove those earlier pieces that have rendered out. Stir every couple of minutes.
I take the fat rendering (1 part) and add it to a beef broth (3 parts) and simmer for about an hour. Then usually freeze it when it is cool.
Have used it for everything from "french dip" to marinate, to injection; works good as a soup base / stock also.