Melt the cheese in the top of a double boiler. (If you do not have a double boiler, you may heat it in a saucepan over low heat, stirring it often, or you may leave it in shredded form; it will give a different look to the finished sausage balls.) While the cheese is melting, brown 1 pound of port sausage in a skillet, stirring continually, until crumbly and all pink is gone. Drain any excess grease from the sausage, and then pour it onto a plate or bowl that has been covered with a few paper towels. Try to absorb as much of the excess grease as possible with the paper towels. Combine the sausage crumbles with the melted cheese, and then add it to 3 cups of biscuit mix. You can use an electric mixer, but I used my hands to get all three components well-combined. Form into 1-inch balls, and place on an ungreased cookie sheet or flat baking pan. Bake at 450 degres for about 8 to 10 minutes. Remove immediately from the oven, and transfer to a serving dish. Serve immediately with sweet dipping mustard. These sausage-cheese balls may be refrigerated or frozen after they are baked. Just pop what you need into a microwave for a few seconds, and it's just like fresh!