what is the best way to get an adult yorkie socialized with an adult cat?

I have two cats and my boyfriend has a dog. We would live together but the dog (a large yorkie) just wants to chase and try to bite the cats.

For up to 20 min.s at a time, put a mesh muzzle on the dog (it is not cruelty if not abused) and put the dog in the same room (under supervision), encourage play between them (with same toys, or food) and do not reward bad behavior. But you have to seriously reward the good behavior even if you provoke it, cause otherwise he will never learn you want him to be nice to them. also try rubbing there scents onto each others things, and on towl you can put out by food dishes, etc. Kind of give them acceptable stimulous toward each other. but always supervise them together. Worst case scenario, they learn to ignore each other politely. Also, if the yorkie won't back down, let the cats defend themselves (Monitered!!!), and he will learn his lesson.

Remember, all dogs and cats have the same basic instincts. Some are rather difficult to train. Just like potty training it will take some time and alot of patience. Try the crate training/water bottle method I use for most of my animals. Give them time facing each other in their own crates several minutes each day increasing several minutes every other day. Then when they are together and the dog chases the cat use a higher powered squirt bottle or gun and squirt the animal in the face telling it "no" at the same time. After a while it will equate the word "no" with the squirt and mind when you just speak the word. All the while you are still reinforcing positive behavior among them by keeping them in their own cages in close proximatey to each other. It is much like having to seperate restless or sqabbling siblings. They will grow on each other in time. Also remember, however, that Yorkies were bred to hunt and catch small animals so chasing the cat is a sport to them and keeps them healthy. You may have to choose eventually because genetically they are not supposed to like cats. I have seen them get along, but each case of course could be different.

its not easy but u shuld seperate them as soon as any signs show that they are ready to attack or are scared

Tina (two comments up) has great advice.