In a crock pot on high add chicken, onion, and seasonings. In a saucepan on the stove add milk, cream cheese, asiago cheese, Parmesan cheese, and butter. On medium heat stir until all the cheese has melted. Pour mixture on top of chicken in crock pot. Keep an eye on this and give it a stir every hour. Add more milk at the end if you want a thinner sauce. The last hour cook potatoes, drain and add to crock pot. Do not over cook potatoes or they will turn to much in the crock pot. You can also add them earlier if you have more time to use the crock pot. I didn't so I used this method.
The last 30 minutes mix your bisquick dumpling mixture together and spoon on top of your chicken. Cover and cook for 30 minutes or until you can toothpick them and the toothpick comes out clean.