Why in some recipes with using caramel, like, for example, caramelized walnuts or chinese caramelized apples, its required to melt sugar in oil or butter instead of making caramel with water or just melt the sugar per se?   typical recipe scheme looks like this:   melt and caramelize sugar in fat  put pieces of food into and cover by this caramel  put the final product to nonsticky surface and let it cool   so, question:  What the role of fat in such recipes? is it possible to use sugar caramelized by itself or with water? or it has influence on covering abilities of caramel? or smth else?  Thank you for your answers and time. 
I am coming rather late to this party, but here's my answer: Caramel made by heating sugar in fat (oil or butter) will never completely harden like caramel made in water or just melting sugar and will get very soft again when reheated. Also, it is much easier to control the color of the caramel when made in fat. In Chinese cuisine there is a process called "Red Braising" (Hong Shou). When red braising meats (typically fatty meats like pork belly), sugar is caramelized in oil until it is red (almost, but not quite brown) and then the meat is seared in the caramel. This gives it a rich, reddish, coating that does not harden. Imagine the dangerous splatter if you put fatty pork belly in a hot caramel made with water! There would be boiling sugar everywhere. Besides, it is very difficult to get red caramel when water or dry cooked. So ... making caramel in oil is called for when you want a red color, or want a caramel that is deeply colored but will not completely harden. But be very careful and make it in a deep pot; splattering caramel is dangerous enough, but add boiling oil to the mix and it becomes doubly dangerous! 